Excellence through equality of opportunity : can increasing the social inclusiveness of education systems benefit disadvantaged students without harming advantaged students?

Middle- and upper-class parents tend to think that school systems in which students from different socio-economic backgrounds learn together in the same schools would promote equality of opportunity but would harm their children. I investigate this belief, making both a conceptual and a methodological contribution. Conceptually I broaden the concept of differentiation in education arguing that not only formal differentiation but also more "hidden" forms of differentiation such as residential segregation or private schools might contribute to a segregation of students from different socio-economic backgrounds into separate schools. Methodologically I contribute to the debate by analysing changes within countries, controlling for time-constant unobserved differences between countries. Using five waves of PISA data for 35 countries from 2000 to 2012, I find that in education systems in which schools become more socially inclusive, students from disadvantaged families improve their performance. Students from better-off families perform well independent of whether the education system becomes more socially segregated or inclusive. Thus, there is no conflict between equality of opportunity and excellence in education. In contrast, excellence can be improved through equality of opportunity without hindering advantaged students or top performers.