This article describes the social and economic “segregation” of students between schools in England, and the likely causes of its levels and changes over time. It involves a re-analysis of the intakes to all schools in England 1989–2011, and shows how strongly clustered the students are in particular schools. The pattern for primary-age schools is the same as for secondary-age schools. However, ... [Show full abstract] each indicator of potential disadvantage—poverty, learning difficulty, first language, and ethnicity—has its own level and pattern of change over time. This suggests that there is not just one process of segregation. The implications for any state wanting a fair and mixed national school system are spelled out.