What is known about the effect of class size reduction on student outcomes?
Research has found that reducing class sizes has a positive effect on student outcomes in the primary (K-3) grades. For example, the Tennessee Student-Teacher Achievement Ratio (STAR) experiment, the only research using a true experimental design to study the impact of smaller classes, found that student performance improves in smaller classes in the primary (K-3) grades, with the gains enduring through later years. After one year in kindergarten, classes with about 15 students performed 5-8 percentile points better on standardized tests than students in classes with 22-24 students. Recent evaluations of Wisconsin’s class size reduction efforts found that students in smaller classes had better test scores than similar students in larger classes. Disadvantaged students benefit more with smaller classes. There is less evidence that smaller classes have much influence on student outcomes in the upper grades or among students who are not disadvantaged in some way. Smaller class sizes help
