Investigating the Impact of Differentiated Instruction in Mixed Ability Classrooms:
It’s impact on the Quality and Equity Dimensions of Education Effectiveness
Valiande A. Stavroula
Cyprus Pedagogical Institute
University of Cyprus
University of Cyprus
Paper presented at the :
International Congress for School Effectiveness and Improvement 2011
Investigating the Impact of Differentiated Instruction in Mixed Ability Classrooms:
It’s impact on the Quality and Equity Dimensions of Education Effectiveness
Valiande A. Stavroula, Kyriakides Leonidas, Koutselini Mary
This paper presents the results of a study concerning the application of differentiated
instruction in mixed ability classes, in which 24 elementary classes of 479 Cypriot pupils
participated. The study provides evidence about the effect that systematic differentiated
instruction in mixed ability classes has on students’ achievement. The results of the
experimental group of the research that had received differentiated instruction were compared
by multilevel regression with the results of the control group that had not received
differentiated instruction. The comparison aimed at investigating the difference in
achievement between the two groups and the identification of other factors that affected
students’ achievement between and within these groups. A multilevel structure equation
model was used to demonstrate the relations and the impact of the change of teaching
practices, monitored by a differentiated instruction observation key, over students’
achievement. Along with the main research question determining the impact of differentiated
teaching on students’ achievement, research results gave substantial evidence over the
dimensions of quality and equity of education effectiveness. Quality and equity dimensions of
education effectiveness consists of main conflict issues for differentiation instruction in mixed
ability classrooms. Based on the results of the study presented, this articles’ main target is to
discuss how differentiated instruction can promote equity and quality for all in mixed ability
Educational effectiveness has been one of the main problems encountered in modern
societies’ educational systems. Research reveals that educational systems fail to meet the
challenge of providing quality and equity, leading to achievement gap (Brooks-Gunn &
Duncan, 1997; De Civita, Pagani, Vitaro, & Tremblay, 2004; Strant, 1999), between different
groups of students. Evidence supports that achievement gap increases during schooling (Fryer
& Levitt, 2004, 2006). These findings declare that education has failed to fulfill its mediating
role and educational systems have not found the way to be effective for all. Narrowing the
achievement gap has been the main aim of socially directed educational systems, in order to
achieve equity. Although many curriculum reforms and policies were formed based on
providing and promoting equity trough enchainment of quality in education, the results of
such efforts around the globe have not been very promising.
Traditional and undifferentiated instructive approaches that do not facilitate the
construction of knowledge for all students in mixed ability classrooms are seen as one of the
basic factors causing this problem (Valiande, 2010). Supporters of differentiation and its
effectiveness state that it is the only way for effective teaching for all students in mixed ability
classrooms (Tomlinson, 1999, 2001; Koutselini, 2006). Differentiation guides the planning
and instruction in mixed ability classrooms based on students and their needs, facilitating the
construction of knowledge for each and every student based on its prior knowledge and
The study presented in this article, is mainly an effort to put differentiation in practice,
by fulfilling the key presuppositions for effective differentiated instruction and evaluating its
implementation and its effectiveness, aiming at finding a way to act in the best interest of all
students in mixed ability classes.
Theoretical Background of Differentiation
The technocratic and positivist tradition that led to knowledge and content oriented
educational practices has raised strong criticism bared to its failure to mediate society’s needs
(Apple, 2003; Guba & Lincoln, 1989; Habermas, 1978; Giddens, 1976). The limitations and
weaknesses of the technocratic tradition bring out the need for new theoretical framework for
educational practices. A theoretical framework, in which students are the center of any
decision and any action to be taken. A theory and practice on how to guide students in their
own learning path. Students are not commodities and schools are not factories producing
specific kind of working units. Differentiation entails a solid proposal of such framework and
is presented as the answer to the limitations and weaknesses of the technocratic tradition
(Valiande, 2010). The theory of differentiated instruction is based mainly on the theory of
social constructivism (Vygotsky, 1978) and emphasizes the active participation of students in
the learning process where the construction of knowledge emerges due to the interactions of
students with their environment (other students, teachers, knowledge, educational material
The teacher, who entails the key to a successful differentiated instruction (Valiande &
Koutselini, 2008, 2009;Valiande, 2010), is challenged to facilitate learning for students of
different readiness level, interests, learning profile (Tomlinson, 2003), socio-economic and
cultural capital and psycho-emotional characteristics, all features that can affect the
construction procedure of new knowledge.
Differentiated instruction that was first proposed as a teaching practice by Tomlinson,
(1999) is seen as the change of the teaching process based on teaching routines that
correspond to the large span of students’ differences in mixed ability classrooms, such as
student’s readiness, interests and learning style (Tomlinson 1999, 2001). Furthermore,
differentiation can be defined as the instructive approach by which teachers modify the
curriculum, their teaching methods, the educational sources used, the learning activities and
the evaluation methods according to and in correspondence with students’ differentiated
needs, in order to maximize the learning opportunities for every student (Bearne,1996).
Differentiation constitutes an innovating, constant reflective procedure of effective
teaching and learning that cannot be met by readymade lesson plans. The planning and the
instructional choices of a lesson plan based on differentiation can only be used effectively
when chosen by the teacher, according to students’ needs and other personal characteristics
(Valiande & Koutselini, 2008, 2009; Valiande, 2010). Students’ learning style, their interests,
their talents, their skills, their competences and their cultural background will guide the
teachers through his final decision concerning the kind of differentiated teaching to be chosen
Although Tomlinson’s proposal for differentiated instruction corrects deficiencies of
the positivist instruction paradigm by imposing a more student-centre instruction model, it
fails, at the same time, to identify and take into consideration several students’ personal
factors that affect and determine learning, such as the socioeconomic status of the family,
students’ level of self-perception and other specific characteristics arising from students’ life
outside school. While differentiation theory calls on equity by responding to students’ needs,
simultaneously education is formed responding to society’s call for the rise of standards,
through strictly countable tests and their results, becoming a means for the reproduction and
the creation of social and academic inequalities (Apple, 2006).
Differentiation proposed and used in this study is based on critical pedagogy shifting
away from positivist and technocratic learning processes (Apple, 2006; Friere, 1978). Critical
differentiation takes differentiation a step further than Tomlinson’s proposal, by focusing
simultaneously on students’ needs and the factors affecting students’ learning in the school
environment and outside school, in order to plan a differentiated learning process accordingly
(Koutselini 2008). Koutselini proposes that differentiated instruction should be seen in the
framework of a meta-modern curriculum (Koutselini, 2006) which offers a critical framework
for the theory and practice of differentiation. In a metamodern curriculum differentiation is
not actually a teaching process but rather a “learning process”, where emphasis is placed on
the interaction of student, knowledge and teacher in an open and flexible learning process
(Valiande & Koutselini, 2009). Differentiated teaching is the learning process in which
students are facilitated to construct their knowledge by maximizing motivation for cognitive
and metacognitive growth that will eventually improve academic outcomes for all students
(Koutselini & Gagatsis, 2003) and strengthen their explanatory faculty.
Differentiated Instruction in the framework of constructivism could be the answer to
the problem of increasing diversity and school failure in mixed ability classrooms.
Construction of knowledge is a unique personal learning process, where each and every
person understands and gains meaning of new knowledge based upon their prior knowledge
and their personal beliefs and needs. In a constructivist learning process where differentiation
is applied, a child-centered teaching approach sees every student as a unique “biography” and
not as a copy of the same picture. Consequently, differentiation is the correspondence to the
needs of each student and the facilitation of construction of knowledge for each and every
student that cannot be considered as a transfer of knowledge (Koutselini, 2006).
Effectiveness of Differentiated Instruction
The theory that supports differentiated instruction has great impact in teaching all over
the world bringing major changes in the way teachers envision and practice teaching.
Although we have witnessed curriculum changes that promote the implementation of
differentiation, literature lacks of substantial research evidence supporting differentiation
theory (Hall, 2002). Research support on differentiation theory is limited and is mainly based
on individual theories, upon which differentiation theory and practice has been developed.
The first attempt on research on differentiation constitutes of a growing number of studies and
small scale research that show and support the enhancement of teaching and learning through
differentiation (Tomlinson, 1999; Good & Brophy, 2003) and provide evidence for positive
effects on students’ achievement (Pfannenstiel, 1997; Chall, 2000; Kim, 2005).
A growing body of research has emerged the last few years concerning the
implementation and effectiveness of differentiated instruction. Most of these studies referred
to specific groups of students, gifted students and students with disabilities (Tieso, 2005;
Baumgartner, Lipowski, & Rush, 2003; McQuarrie, McRae, & Stack-Cutler, 2008 ; Rock,
Gregg, Ellis, & Gable, 2008; Geisler, Hessler, Gardner & Lovelace, 2009) or focused on the
implementation of differentiation and teachers’ attitudes towards differentiated instruction
(Tomlinson, 2001; Tomlinson, Moon & Callahan, 1998; Blozowich, 2001; Brimijoin, 2002;
Johnsen, 2003). Only a small number of studies investigate the effectiveness of differentiation
on the whole and under certain conditions, showing the precedence in academic outcomes of
students that were taught by differentiated instruction (Gayfer, 1991; McAdamis, 2001). The
present study, contrast to previous studies on differentiation, examines the implementation
and effectiveness of differentiated instruction for all students and at the same time evaluates
it’s power to bring equity and quality in education effectiveness.
Equity and Quality dimension in differentiated instruction
Equity in education has become a common concern with a focus on positive attempts
to achieve equity in different educational systems (Moreno Herrera & Francia, 2004). With
mixed ability classrooms being more diverse than ever by the increase number of students
from several ethnic races and cultures, students with different ability and readiness levels,
special education students and students from different socioeconomic background,
educational equity gains new meaning and is more prompt than ever. A big part of
educational research all over the world aims at identifying effective instructive methods for
mixed ability classrooms since mixed ability classrooms are perceived as the means to
promote equity. Equity has been misinterpreted. Equity cannot be exhausted through the
provision of equal opportunities as “a matter of dividing educational, and education-related,
resources more equally or fairly” (Lynch, 2000) nor can it only apply as equal treatment for
students in order to reduce discrimination. Equality in access to educational material and the
equal treatment of students can only be a start towards equity itself, since equity must be seen
in a more holistic way promoting simultaneously equity of results and equity of access,
treatment and opportunity.
Equity in education can be achieved by teaching students corresponding to their level
of readiness, their interests and their learning style, maximizing their opportunities for
personal learning and growth (McLaughlin & Talbert, 1993). In this framework, equity in
education and social justice can only be met if teachers find the way to correspond to the
diversity of their students (Gamoran & Weinstein, 1995) through differentiated instruction.
One can state that equity is the opportunity all groups of students have in a mixed ability
classroom, in achieving the maximum concerning the goals of the curriculum, according to
the personal abilities and competences of each student ensuring equal access to knowledge.
In the existence of a growing achievement gap one can suppose that equity in
education has not been met. Apple (2006) supports that this is a result of the commodification
of education that brought unequal access to quality of education. Researches justify the
creation of the achievement gap as a result of students’ social inequalities, differences
between genders and differences between students’ ethnic races (Strand, 1999). These
students’ characteristics, by which students are grouped in order to be studied, are not clearly
and uniquely identify, as there is an overlapping of students’ groups because of common
characteristics between group members from different groups. For example we cannot and
should not assume that underperforming students always come from disadvantage family,
from a specific students group (specific ethnic group or a specific SES group). That’s why the
whole picture as a synthesis of its details that will lead us to a realistic picture of student’s
needs must guide every teacher, in order to find ways to be effective for all. The dynamic
character of Differentiated Instruction theory provides the teacher with a framework for his
instruction by which ensures both quality and equity dimension of effectiveness. Evidence to
support differentiated instruction’s ability in promoting equity and quality dimension of
effectiveness will be presented later on in this article.
If we define quality dimension of educational effectiveness, as the quality of
instruction provided to all students which effectively supports their personal learning and
leads them to higher achievement levels, we can assume that equity dimension is met
simultaneously. Equity dimension of effectiveness is accomplished if quality instruction
allows all students to pursuit personal higher attainment according to their own knowledge,
dexterities and competences. Willie finds that quality and equity can and must be interlinked
and by doing so “education, should focus neither on cultivating excellence at the expense of
equity nor on cultivating equity at the expense of excellence. In a well-ordered society, the
goal of education is to seek both excellence and equity because they are complementary. One
without the other is incomplete” (Willie, 2006).
The lack of equity dimension of effectiveness can be closely linked to differential
school effectiveness. Even though research findings on differential school effectiveness are
mixed and contrary, several studies show differential effect in relation with prior knowledge
and ethnicity (Nuttal, Goldstein, Prosser, & Rasbash, 1989; Thomas Sammons, Mortimore &
Smees,1997; Tomlinson, 1999) with the more consistent evidence revealing differential
school effects relating to prior achievement (Jesson & Gray, 1991; Sammons, Nuttall, &
Cuttance, 1993; Campell, Kyriakides, Muijs, & Robinson, 2004; Kyriakides, 2004). Most of
the studies on differential effects examine the differential effect between schools and are
mainly concerned with the investigation of achievement gap between schools, paying little
attention to the extent teachers and school perform consistently for all students’ group
(Kyriakides, 2004). As Strand (2010) supports, there is a need for studies with focus on with-
in school gaps in order to identify, study and understand the factors affecting the achievement
gaps that simultaneously formed and increase equity gaps.
Education effectiveness research major aim through the years was to identify and
determine the characteristics of effective teaching that will provide all students with equal
opportunities (Kyrikiades, 2007 ). Most of these studies tried to create an effective
instructional model with a “generic way” of effectiveness for all students (Cambell at al.,
2004). Although the determination of an effective model for all will be ideal, this could not be
the case considering that instruction in mixed ability classrooms means dealing and
instructing students from different cultures, different learning styles and personalities,
different socioeconomic status and other characteristics that needs to be encounter. Research
has shown that specific instruction characteristics can be more or less effective with specific
group of students (Stenberg, 1988; Dunn, Griggs, Olsen, Beasly, & Gorman; Kyriakides,
2005; Creemers & Kyriakides, 2006). The results of studies on effectiveness support that
specific teaching characteristics impose a differential effect on different group of students,
inducing the need to identify general characteristics of differentiated instruction that will
allow the teacher to adopt his teaching according to the characteristics of different students’
groups in his classroom in way that learning will be supported for all, without favoring
Differentiation seeks to bring quality in education without the creation of differential
effectiveness, since differentiation should maximize the effectiveness for all and as thus allow
for equity dimension of effectiveness to be accomplished. As the theory of differentiation
supports both quality and equity of effectiveness, the present research is seeking for evidence
to support this statement.
This article, studies a) the effects of differentiated instruction on students achievement
in mixed ability classrooms and b) the dimensions of quality and equity effectiveness of
differentiated instruction, implemented by Cypriot teachers in order to improve their
effectiveness. Although the Cypriot curriculum supports the theory and practice of
differentiated instruction and differentiated instruction was set by the Cyprus Primary
Education Department as the official aim of primary education for the school year 2002-2003,
almost none or little change has been made by teachers on their teaching practices towards
differentiation. Our research has shown that this is not allocated to teachers believes
concerning the effectiveness of differentiation. Ιn contrast this is due to their lack of
knowledge and training on differentiated instruction practices and the lack of support,
differentiation material and time to organize differentiated instruction (Valiande, 2010).
This study had three basic aims. The first aim was to determine whether findings from
the research provide substantial evidence for the effectiveness of differentiation in mixed
ability classrooms. The effectiveness of differentiated instruction and its effects on students’
achievements is being supported by studies concerning specific groups of students, gifted
students and students with disabilities (Baumgartner, Lipowski, & Rush, 2003; Tieso, 2005;
McQuarrie, et al. 2008; Rock, et.al 2008; Geisler et al.2009). Only a limited number of
studies investigate to a certain extent the effectiveness of differentiation for all students in
mixed ability classrooms (Gayfer, 1991; McAdamis, 2001).
A second aim was to determine the characteristics of effective differentiated
instruction by using and testing the observation key for differentiated instruction (Valiande,
2010). The observation key is based on the educational literature, of the last decade, on
differentiation (Tomlinson, 1999; Koutselini, 2006, 2008) by which effective differentiation
teaching practices and procedures are being presented mostly on a theoretical basis. The main
aim was to test differentiated instruction characteristics as implemented by teachers in their
classrooms, that participated in the study, and at the same time investigate the effects of those
characteristics on the quality of teaching and students’ achievement.
A third aim was to evaluate the equity and quality dimension of differentiated
instruction based on the results of effectiveness of differentiation for different group of
students. Although differentiated instruction is based on the assumption that all students’
learning is supported by taking into account all different aspects of their needs and
competences, this is still something that has to be proven. In order to investigate and
determine the equity and quality dimension of effectiveness by differentiated instruction, the
existence of a differential effectiveness by differentiation was investigated.
The study presented in this article was contacted during the school year of 2008 -2009
in Cyprus primary schools. Convenience sampling was used to select elementary classes
(n=24) that participated in the study. The pupils (n=490) who attended the 24 Year 4 primary
classes and the volunteer teachers (n=14) that differentiated their instruction constitute the
sample of the study. The experimental group of the study was formed by the students of the
14 classes that received differentiated instruction. The control group was formed by the other
10 classes that accepted to participate in the study. The teachers of the control group did not
receive any training or support on differentiation throughout the research and did not
differentiate their instruction in any way. All the thirteen schools participated in the study
were situated in Nicosia Educational District.
Fourteen volunteer elementary teachers teaching in Year 4 primary school classrooms
started training on the theory and practice of Differentiated Instruction from the previous
academic year (April 2007-2008). The researcher planned training seminars for educating and
preparing participant teachers to implement differentiation in their every day teaching
practice. The training provided teachers with knowledge concerning the main aspects of the
differentiation theory and most important helped them to understand how to translate
differentiation theory into practice by realizing the main axes of differentiated instruction.
Teachers learned how to design a lesson plan based on differentiated instruction theory and
most important they learned how this lesson plan can be modified reflectively according to
upcoming needs of their students. As differentiated instruction is a highly reflective
procedure, it is at the same time strongly depended on teacher’s sufficient preparation that
will give him the relative options to maneuver the lesson reflectively.
Although teachers were given several lesson guides that were adopted accordingly to
students’ needs, teachers cooperate with each other and with the researcher in preparing
differentiated lesson guides based on the Cypriot curriculum and the book of year 4 primary
school classes. All teachers used these lesson guides in order to achieve an overall consensus
of what was taught in all the classes participated in the study. Lesson guides were shared to all
teachers through a web site created especially for this research. The participant teachers
continued to receive training and support all through the research. Immediate feedback was
given to the teachers by the researcher and a discussion followed the observed lesson in order
to help the development of teachers in differentiating their instruction. Furthermore, an online
forum was created that gave teachers the opportunity to exchange ideas and share their
thoughts with the whole team of teachers participating at the research. The researcher was
able through the forum and her personal email to address all the problems and the questions of
Multiple sources of data collection were used in this study in order to answer the
research questions. Evaluation of students’ prior attainment and their educational progress
was made by written tests, a literacy test and a test to determine students’ comprehension
level. Both tests were administered to all the Year 4 students of the twenty four classrooms
participated in the research (N =490) twice: (a) at the begging of school year and before the
introduction of differentiated instruction (October, 2008) and (b) at the end of the
implementation of differentiation instruction (May 2009). Therefore, I could compare the
attainment of students of the experimental group that were taught by differentiated instruction,
before the introduction of differentiated instruction and at the end of its implementation with
the attainment of students in the control group classrooms which did not received
differentiated instruction in the corresponding tests.
Information about students’ family socioeconomic status was collected through a
questionnaire completed by the parents. Quality of differentiated teaching was measured
through an observation key for differentiated instruction used for reporting on lesson
observations by the researcher. The observation was developed based on Koutselinis’ work on
the characteristics of differentiated Instruction (Koutselini, 2006b, 2008) and consisted of 18
statements-questions about the basic characteristics of effective differentiation instruction in
Effectiveness of Differentiated Instruction
The effectiveness of differentiated instruction was investigated separately for each test
with multiple regression analysis. Investigation of the extent to which students’ factors, such
as education and occupation of father and mother, gender, student’s group (experimental or
control group), students’ socioeconomic status and their prior achievement in both literacy
and comprehension tests can predict student’s achievement was contacted by multiple
regression analysis (MRA). Stepwise method was used for both analysis and all students’
factors as presented above entered the analysis. Models created by the two multiple
regressions are presented in Table 1.
d. Predicting Variables in the Model: Students’ achievement in literacy pre test, Students
group (control/experimental), Students’ achievement in comprehension pre test.
As shown in Table 1, model 1 and model 2 of multilevel regression analysis for both
tests show that prior achievement in pre testing and differentiated instruction are the main
predicting variables for students’ achievement. Fathers’ university education which was the
only family factor entered in model 3 for the comprehension test has a minor predicting value
Model summary of Multiple Regression analysis, , correlation coefficient R and R², Adjusted
correlation coefficient R² for the comprehension test and literacy test (N=490)
Model R R² Adjusted R
1 0,570a 0,325 0,324
3 0,653c 0,426 0,422
1 0,629a 0,39 0,394
a. Predicting Variables in the Model: Students’ achievement in comprehension pre test /literacy
b. Predicting Variables in the Model: Students’ achievement in comprehension pre test/literacy
re test, Students group (control/experimental)
c. Predicting Variables in the Model: Students’ achievement in comprehension pre test,
Students group (control/experimental), fathers university education
and it’s not taken into consideration. Prior achievement in comprehension test adds to the
model for the literacy tests (model 3).
These results show that students’ prior achievement and their group (experimental or
control group) explain to some extent student’s achievement in post test. In the analysis of the
comprehension test students’ prior achievement and their group interpret (R ²) 42% of the
variance of students achievement in post comprehension test. Each of the predicting variables
had a significant (p < .01) zero-order correlation with students’ post achievement. Similar to
these results are the results of the literacy test, where prior achievement of students in literacy
test, students’ group and students’ prior achievement in comprehension test interpret (R ²)
54% of the variance of student achievement in literacy post test. The three regression models
according to the criterion t appear to be statistically significant (p <.05) with a weighted
constants of Var 1(prior literacy ach.) = 0.49, Var2(students’ group)= 0.34,
Var3 (prior ach. Comprehension) =0.23.
The correlation between students’ group (experimental or control group) and post
achievement in comprehension test is represented in graph 1. The difference between the
average students’ scores of the experimental group and the control group for the
comprehension test is shown by the slope of the achievement line. Experimental group’s
achievement line is greater than the slope of the achievement line of the control group,
suggesting that progress in the experimental group was significantly higher than the progress
of the control group in the comprehension test even though the achievement of the control
group in comprehension pre test was lower than that of the experimental group.
Graph 1: Graphical representation of students’ achievement in pre and post comprehension
test of the experimental and the control group
Although the effect of family factors on students’ achievement was identified on prior
achievement the same effect is not being identified in the multiple regression analysis. This is
due to multicolineartity of variables in the regression analysis and can be mainly explained
based on the idea that family factors affect students’ achievement indirectly through students’
These results show that no other factor contributed to the change in student’s
achievement, further than the intervention of differentiated instruction. Furthermore, it is
shown that with-in the experimental group there was none specific group of students that were
favored or disadvantaged by differentiated instruction. On the contrary, students achievement
from all groups of students (socioeconomic group, achievement group and groups
characterizes by other family factors) was higher in both tests (comprehension test and
Equity dimension of Differentiated Instruction
As mentioned above, variables concerning students’ family characteristics and
students’ SES did not enter in any of the regression models due to multicolinearity of
variables. The indirect effect of SES on students’ achievement in the post test and especially
the reduction of this effect by the intervention of differentiated instruction has been further
investigated in order to determine its existence and its effect on students’ achievement. From
a regression analysis performed to determine the predicting value of student’s prior
achievement on students’ achievement on the post test, the values of non-weighted residuals
were extracted that show the difference in students’ achievement between the pres and post
test. Then two multiple regression analyses were conducted in order to determine the degree
of impact of SES on students’ progress in the two groups of the research (experimental and
control). Both analyses generated similar results, with the multiple regression model of the
experimental group showing a regression coefficient (R ² = 0.064) lower by 1.1% compared
to control group regression model (R ² = 0.075) (table 2). The difference between the two
models is too small to answer our research question and thus it was necessary to further
investigate this research question.
Table 2: Correlation Coefficient R, Regression coefficient R ² and Statistical Adjusted
regression coefficients of prediction model for students’ progress (control and experimental
group) in literacy test in relation with their SES
Model R R²
Square df F sig
Experimental Group 0,274 0,075 0,070 1 16,008 0,001
Control Group 0,252 0,064 0,060 1 18,754 0,001
a. Variable Participating: SES
In order to investigate further the effect of SES on students’ progress, one- way factor
analysis of variance (One-Way ANOVA) was conducted on the experimental group literacy
test data. The variance of the difference in students' achievement in the literacy test was
explored based on regression unstardized residuals for the categories of SES. While a factor
analysis of variance was found to be significant (F = 3,130, p = 0.015 df = (4,255), multiple
comparisons between categories of SES for criterion Post-hoc Scheffe revealed that no
statistically significant difference exists between different SES categories, leading to the
conclusion that differentiated Instruction did not favor students from certain social groups.
In contrary, one- way factor analysis of variance (One-Way ANOVA) for the control
group showed a statistically significant difference in the variation of the change in students’
achievement in the categories of SES (F = 7,369, p <0.001, df = (3,256)). In further
investigation through, multiple comparisons of the categories with post-hoc Scheffe criterion
revealed a statistically significant difference in average change of students’ achievement from
lower socioeconomic families in relation to the change of students’ achievement of upper
middle socioeconomic families. Statistically significant differences were also found between
the average change of students’ progress in middle and upper middle socioeconomic families.
Differentiated Instruction, as shown by the above results, contrary to traditional
teaching, which adversely widens the achievement gap between students of different social
background, accomplished in a short period of time to maintain the opening of the
achievement gap between students from different socioeconomic background. Although this
result does not show the narrowing of the achievement gap, it reveals the potentials that
differentiated instruction has in leading to the narrowing of the gap if implemented with
consistency over a longer period. Implementation of differentiation in this study has made a
big step in facing the negative effects of socio-economic factors on students’ achievement, by
managing diversity effectively, providing learning opportunities for all students from all
socioeconomic groups something that did not occur in the control group.
Differentiated Instruction Characteristics
In assuring the consistent implementation of differentiated instruction by all teachers
participated in the research and in order to identify the characteristics of their instruction,
observation key was created and used by the researcher to observe the instruction process of
the fourteen teachers. The observation key was created based on the main characteristics of
differentiated instruction (Koutselini, 2001, 2006) and consisted of 18 criteria on a 5 points
likert scale. For the validation of the observation key initial values for each criterion were
equated through rasch, in order to equated the degree of difficulty in implementation of each
criterion between the first and second observation and thus determine the degree of its
difficulty. Out of the 18 criteria of the observation key, 13 criteria was able to be equated.
The estimates in logits for the thirteen are shown in Table 3 and refer to differentiated
instruction characteristics that could be applied by the teachers in a high frequency and
without any difficulties (0 - (-3) or appear less frequently and with difficulty (0 - 3).
Table 3 :
Codigs and Estimates in logits for Differentiated Instruction Observation Key Criteria
Time the teacher uses for comments on student’s general behavior and way
of working during teaching -2.13
Time the teacher uses to more explanations and examples during teaching
Time the teacher uses for direct teaching or asking questions during teaching -1.27
Degree of activities variation during teaching -1.02
Extent to which the teacher provides students with personalized support and
help during teaching -0.89
Time the teacher uses to provide students guidelines for their work during
Extent to which opportunities are given to students from all readiness levels
to participate in the learning process 0.58
Degree of opportunities given to students to restore basic knowledge and
Degree of opportunity given to students to recover prerequisite knowledge
during teaching 0.82
Extent to which lesson activities are prioritized 1.05
Degree of control over the accomplishment of the lessons’ objective during
Extent to which the individual work of students varies based on their interests
and talents 1.18
Extent to which the teacher differentiates students’ homework 1.89
Further analysis was conducted for the initial and final values of the observations
based on 2 variables, the key criteria for differentiated instruction as shown in Τable 3 and the
data gathered from lesson observations of teachers based on the key criteria of differentiation.
The statistical values of the analysis on Differentiated Instruction observation key using the
Rasch model are presented in Table 4. The reliability values of the model, both in relation to
the criteria of the observation key and the values gathered for teacher’ observations, (initial
and final) are as high ranged from 0.81 to 0.88.
Fit indices emerged by using the Rasch model to analyse the data of the observation
instrument for Differentiated Teaching
Parameters Initial Values Final Values
Mean Criteria 0 0
Teachers -0.12 0.18
Standard Deviation Criteria 0.94 0.93
Teachers 0.89 0.79
Criteria 0.82 0.81
Teachers 0.88 0.85
Mean infit mean square
Criteria 1.03 1.04
Teachers 1.02 1.03
Mean outfit mean square
Criteria 0.98 1.01
Teachers 1.06 1.05
Infit t Criteria 0.04 0.03
Teachers -0.02 0.06
Outfit t Criteria 0.08 0.07
Teachers -0.05 -0.08
A comparison of the initial mean value (-0.12) and final mean value (0.18) of the
observation key with a constant mean of 0, indicates that teachers were able to change their
teaching based on the criteria of Differentiated Instruction observation key, increasing the
mean value on the observation key up to 0.30 logits. Values of the model Mean infit mean
square and Mean outfit mean square are very close to 1 and values for infit and outfit the
range -0.08 - 0.08, values are close to 0, giving validity and reliability to the observation key.
Based on these data, the observation key comprises a valid and reliable research tool that can
be used for the observation of differentiated instruction. Simultaneously, these results answer
one of the research’s aims by describing the way and the degree of differentiated instruction is
implemented by the teachers in order to meet the diverse needs of their students.
Effect on quality of differentiated Instruction on students’ achievement
The data concerning the change in the quality of teaching, as presented above, resulted
in the creation of a theoretical model (Figure 1) in order to study and determine the effect of
the change in teaching practices on students’ achievement. Based on the theoretical model, a
Multilevel Structure Equation Model was created. The results of the analysis of structural
equations, confirms the hypothesis of the effect of change in teaching, which was based on
differentiated instruction, on students’ final achievement. Effect values and statistical error
(in brackets) of the variables participated in the model are presented in diagram 1.
Diagram 1: Multilevel Model Analysis (Multilevel SEM) the effect of variables at class level
and the level of student performance in general literacy tests (Greek Language).
The effect of change in teachers’ instruction on students’ final achievement was
calculated at 0.18, which is considered as a small effect. Similarly, the influence of the initial
performance of the class (0.25) on class final performance indicates that the improvement of
the mean achievement score of the classroom is related to the class initial achievement mean
score. Moderate effects were observed by students’ socioeconomic status over their initial
achievement (0.22). While initial student’s achievement, on student level of multilevel SEM,
show to have a major impact on student’s final achievement (0.61) concerning each student
separately. According to multilevel SEM results presented above, modifying and
improvement of teacher’s instruction based on the theory of differentiation bring similar
improvement in students’ achievement. The smaller the change in teachers’ instruction, the
smaller the effect in students’ achievement and progress. Even though the effect size of
differentiated instruction on students’ achievement is minor, this does not consist of problem
in supporting differentiation as an effective teaching practice, considering the limited time of
the intervention for the implementation of differentiated instruction and the conditions under
which the intervention took place, while teachers were still in a learning process on how to
differentiate their instruction.
Based on the theory and practice of differentiation this study responded to its
fundamental objective in providing evidence to support the theory of differentiation, its basic
principles and presuppositions, and confirm its effectiveness in mixed ability classrooms.
These findings provide the educational scientific world, with the empirical data required
(Hart, 1992; Kronberg, York-Barr, Arnold, Gombos, Truex, Vallejo & Stevenson, 1997;
Tomlinson, Kalbfleisch & Layne, 1998; Conway, Arthur-Kelly & Pascoe, 2004) to support
the effectiveness of differentiation for all students in mixed ability classrooms.
Change in quality
on literacy test
on literacy test
Differentiated Instruction in mixed ability classrooms was possible through systematic
training and support, provided to teachers that participated in the study in order to implement
differentiation in their every day instruction. Core instruction principles of effective
differentiation are defined to be the following: the instruction planning based on
constructivism learning theory, the hierarchical order of learning activities, the maximization
of students active participation in the learning process, the reduction of teachers talking time
during teaching, the variety of activities, the students work according to their personal pace,
the personalize support to students, the differentiation of activities according to students’
interests and the learning profile and continuous evaluation of students’ achievement with a
parallel evaluation of the effectiveness of learning process. Training and support for teachers
has proved to be a key to the successful implementation of differentiated instruction by
teachers and it is defined as a basic need for effective implementation and the reason for the
failure of implementation of differentiation in a similar study (Callahan, Tomlinson, Moon,
Brighton, & Hertberg, 2003).
The documentation of the effectiveness of differentiated instruction of language
course in mixed ability classrooms confirms views of other research attempts on
differentiation, according to which, differentiation can be effective for all students regardless
of their readiness level, their gender or their socioeconomic status (Tomlinson, 1999; Gayfer,
1991; Koutselini, 2006). Although effectiveness of differentiation consisted the main aim for
a number of previous studies, most of these studies target group was: specific groups of
students (talented of disabled), a small number of students in a specific area of a subject, for a
very limited time based on a certain focus (Baumgartner et al., 2003; Tieso, 2005; Geisler,
et.al., 2009). The present study and its results concern the whole classroom population for a
whole school year in the instruction of language providing valid evidence that differentiation
is plausible and effective for all students in mixed ability classrooms.
Quantitative data, as presented in detail above indicate a statistically significant
difference between students’ achievement taught by differentiated instruction and students
that that did not received differentiated instruction. Difference between the two students
groups through two separate regression analysis one for each language tests (literacy and
comprehension tests) led to the creation of prediction models for students’ final achievement.
Students’ group (experimental or control group) and students’ prior achievement participated
in the models, where variables like gender and variables for students’ socioeconomic
background (parents education and parents education) that failed to enter the models and were
not capable of increasing the prediction power of the models.
The effect size of differentiation on students’ achievement on literacy test was
estimated at 0.34 and the corresponding effect on the comprehension test was estimated at
0.31. Although the effect size for both tests is fairly small these results were to some extent
expected. The intervention for the implementation of differentiated teaching lasted only 6
months. During these months, an effective intervention could only make a limited difference
to students’ achievement and thus no dramatically differences were expected in the effect
size. Previous research on effectiveness on differentiation supports that its effects are not
immediate and may not be visible before some years of its implementation (McAdamis,
2001). Ann Hess (1999) describes the process of implementing differentiation as an ongoing
evolutionary process and argues that for differentiation instruction to become a teacher’s
permanent instruction practice will need up to seven years.
Effectiveness of differentiation in teaching language courses show by the present
research to constitute an answer to the question raised by Hodge (1997), whose research on
the effects of differentiation on students achievement showed that differentiation improves
students’ achievement on standardized mathematics tests but this did not happen for language
standardized tests. The results of this study answer Hodge’s (1997) question whether
differentiation can be effective for teaching language.
The positive change in students’ achievement has shown that differentiation can be
considered as an effective theory of learning in mixed ability classrooms. Triangulation of
data and methods was achieved in this study providing further validity and reliability to the
research results. Effectiveness of differentiation has been found comparing the achievements
between the control and the experimental group and at the same time the quality of
differentiated instruction has been proved to have an effect on students’ achievement.
Showing the effectiveness of differentiation is very important but perhaps one of the
most important finding of this study is the confirmation of the social-oriented character of
differentiation and differentiated instruction. Although the socioeconomic status of students
was correlated with the initial performance of students, there was no effect of SES on
students’ progress, confirming that differentiation can maximize learning outcomes for all
students regardless their socioeconomic background (Koutselini, 2008). Furthermore, the
evidence found through the one- way factor analysis of variance (One-Way ANOVA) show a
statistically significant difference in the variation of the change in students’ achievement in
SES’s categories for the control group that was not instructed by differentiated instruction.
The same analysis contacted for the experimental group did not show any statistical difference
in the variation of students’ change in achievement.
Based on this evidence, effective differentiation has accomplished to promote equity
dimension of effectiveness by providing all students with the opportunity to improve their
achievement regardless their SES. Differentiated instruction implemented by teachers in the
experimental group managed in a small period of time of the intervention to maintain the
achievement gap size stable in contrast with the control group where the achievement gap was
increased supporting evidence of previous research that achievement gap increases during
schooling (Phillips, Grouse, Ralph, 1998; Strand, 1999; Fryer & Levitt, 2006). A longitudinal
survey contacted in Cyprus provided evidence of the progressively negative school impact on
students’ achievement and the year by year increase of the achievement gap (Kyriakides, et.
al., 2008). The results of the present study concerning the control group are in line to the
These results confirm one of the basic axes of differentiation theory, by which
differentiation is the answer to education call for social and educational equality (Gamoran &
Weinstein, 1995; Ducette, Sewell, & Shapiro, 1996; Darling-Hammond et al., 1999;
Schoenfeld, 1999; Koutselini 2006b, 2008; Valiande & Koutselini, 2008, 2009), providing all
students with opportunities for personal development regardless of their socioeconomic status.
Differentiation has in chorus accomplished to promote the quality dimension of
effectiveness. Although quality dimension of effectiveness can be assumed by the positive
results on students’ achievement that were taught by differentiated instruction, the results of
the multilevel SEM supports further the existence of an effect of quality differentiated
instruction in students’ achievement. According to the findings of multilevel SEM, quality of
differentiated instruction corresponds to the degree of effectiveness over students’
achievement. Quality of teaching accomplished by differentiated instruction is omitted to all
students providing them the help they need to improve based on their personal strengths and
needs, leading to equity in results by improvement in achievements for all.
In the Cypriot educational context, the findings of the study provide a comprehensive
proposal to address educational inefficiency. An implementation of differentiated instruction
based on the main characteristic of effective differentiated teaching as shown by the present
study can enhance the learning process and improve students’ achievement. Differentiation is
not the easy way out of ineffectiveness but we know that it constitutes a proposal for
achieving effectiveness for all students. Differentiation is feasible, effective and necessary in
order to promote quality and equity dimensions of effectiveness based on the evidence of the
research presented. Of course, there is still a long way for research in order to determine
through longitudinal studies the effectiveness of differentiation over time, for all students, in
different educational levels (primary, secondary) and across subjects.
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