- 43% of variation in mathematics achievement is attributable to schools and classes (equally distributed among the two). When students background characteristics are controlled for, about half of the initial variation in schools and classes is reduced.
- School composition variables account for much of the initial importance of school process variables. The joint effect of school composition and school process best explains students mathematics achievement.
- School composition variables, namely, the ability level of the school – have an independent, positive effect on achievement, and more able students benefit most.
- High ability students from low SES families are most sensitive to school composition.