At the eighth grade level, lower class sizes improve the school social environment, which in turn leads to higher achievement. Wenglinsky found that the largest positive effects on mathematics achievement occurred in districts where there were below average socio-economic students. Interestingly, he also found greater achievement gains in districts where teachers' salaries were higher. An overall pattern found in the research indicates that if class size is reduced from substantially more than 20 students per class to below 20 students, the related increase in student achievement moves the average student from the 50th percentile up to somewhere above the 60th percentile. For disadvantaged and minority students the effects are somewhat larger.
Smaller classes make a difference for a variety of reasons.
Higher student achievement in smaller classes may result from alteration in the classroom environment. Teachers report that the classroom atmosphere is better, that students can receive more individualized attention, and that teachers have more flexibility to use different instructional approaches. Teachers find themselves with more classroom space because they are using the same classrooms with fewer students. They also have more time to devote to working with students and parents outside the classroom. The classroom situation changes when there are fewer students to distract each other.