Our longitudinal research findings from one-way and two-way dual language enrichment models of schooling demonstrate the substantial power of this program for enhancing student outcomes and fully closing the achievement gap in second language (L2). Effect sizes for dual language are very large compared to other programs for English learners (ELLs). Dual language schooling also can transform the experience of teachers, administrators, and parents into an inclusive and supportive school community for all. Our research findings of the past 18 years are summarized here, with focus on ELLs' outcomes in one-way and two- way, 50:50 and 90:10, dual language models, including heritage language programs for students of bilingual and bicultural ancestry who are more proficient in English than in their heritage language.