The associations between students’ mean ability levels and the social composition of schools, on the one hand, and the differences between schools of different tracks, on the other, suggest that different school environments also constitute differential developmental environments. Differences in school environments in tracked school systems are not attributable solely to ability grouping, however. They are also produced by institutional factors: track-specific didactic traditions and teacher training programs result in track-specific learning and teaching environments. This study aims to disentangle compositional and institutional effects and to determine what counts at school. Furthermore, it tests for interactions between social composition variables and school track.

Keywords
differential developmental environments, school structure, “Hauptschule”, student achievement, fan-spread effect