“The results … provided convincing evidence that all types of students (e.g., low, medium, and high achievers) benefit from being in small classes (in early grades) across all achievement tests…. in certain grades, in reading and science, the cumulative effects of small classes for low achievers are substantial in magnitude and significantly different from those for high achievers. Thus, class size reduction appears to be an intervention that increases the achievement levels for all students while simultaneously reducing the achievement gap.”
"Results show that smaller classes in 8th grade lead to improvements in non-cognitive skills like student engagement, persistence and self-esteem that have been strongly linked to success in schools and later in life. The authors estimate that in urban schools, the economic benefits from investing in smaller classes would be nearly twice the cost."