Are Effects of Small Classes Cumulative? Evidence From a Tennessee Experiment

Some scholars argue that the effects of small classes in the early grades are not cumulative—that the benefits of small classes accrue in the 1st year of small classes. That argument suggests both policy implications and scientific questions of why additional benefits should not accrue from additional exposure to small classes. In this article, the cumulative effects of small classes on achievement were investigated with data from Project STAR, a 4-year, large-scale randomized experiment on the effects of class size. Controlling for achievement in the previous-year small classes in Grades 1, 2, and 3 yielded additional positive effects on reading and mathematics achievement. Thus, there are additional (cumulative) effects of small classes after the 1st year that may be large enough to be important for education policy.