Are effects of small classes cumulative? Evidence from a Tennessee experiment

Some scholars argue that the effects of small classes in the early grades a re not cumulative-that the benefits of small classes accrue in the 1st year of small classes. That argument suggests both policy implications and scie ntific questions of why additional benefits should not accrue from addition al exposure to small classes. In this article, the cumulative effects of sm all classes on achievement were investigated with data from Project STAR, a 4-year, large-scale randomized experiment on the effects of class size. Co ntrolling for achievement in the previous-year small classes in Grades 1, 2 , and 3 yielded additional positive effects on reading and mathematics achi evement. Thus, there are additional (cumulative) effects of small classes a fter the Ist year that may be large enough to be important for education po licy.