Ability grouping:
The academic benefits are clearest for those in the higher ability groups, but students in the lower groups are not harmed academically by grouping and they gain academic ground in some grouping programs.
That’s the conclusion from Meta-analytic Findings on Grouping Programs – James A. Kulik, The University of Michigan; Chen-Lin C. Kulik, The University of Michigan; 1992. Here’s the abstact:
Meta-analytic reviews have focused on five distinct instructional programs that separate students by ability: multilevel dasses, cross-grade programs, within-class grouping, enriched classes for the gifted and talented, and accelerated classes. The reviews show that effects are a function of program type. Multilevel classes, which entail only minor adjustment of course content for ability groups, usually have little or no effect on student achievement. Programs that entail more substantial adjustment of curriculum to ability, such as cross-grade and within-class programs, produce clear positive effects. Programs of enrichment and acceleration, which usually involve the greatest amount of curricular adjustment, have the largest effects on student learning. These results doe not support recent claims that no one benefits from grouping or that students in the lower groups are harmed academically and emotionally by grouping.
This is a relatively old report. I’m not sure if its conclusions have been rejected by more recent research.
The full article is here.
Cost of College 