- International research supports the conclusion that having high-ability/high-achieving schoolmates/classmates is associated with increased achievement.
- Suggests that ability grouping with curriculum differentiation increases the achievement gap.
- There is a stronger link between students’ social backgrounds and their achievement in educational systems with more curriculum differentiation and in those with earlier placement in differentiated educational programs as compared with others.
- Studies of tiered systems are quite consistent in suggesting that attending higher level schools is positively related to achievement gains and that attending lower level schools is negatively related to achievement gains. Such effects are often found over and above those related.
- Multicountry studies tend to lend clear support to the contention that ability grouping with curriculum differentiation is related to increases in the achievement gap.
- Findings from international research support US research suggesting that ability grouping increases the achievement gap through influencing the social class composition of the classrooms in which higher and lower ability students learn.
- Ability grouping with curriculum differentiation undermines the achievement of initially lower achieving students.