Reduction of class size to increase academic achievement is a policy option that is currently of great interest. Although the results of small-scale randomized experiments and some interpretations of large-scale econometric studies point to positive effects of small classes, the evidence has been seen by some scholars as ambiguous. Project STAR in Tennessee, a 4-year, large-scale randomized experiment on the effects of class size, provided persuasive evidence that small classes had immediate effects on academic achievement. However, it was not clear whether these effects would persist over time as the children returned to classes of regular size or would fade, as have the effects of most other early education interventions. This article reports analyses of a 5-year follow-up of the students in that experiment. The analyses described here suggest that class size effects persist for at least 5 years and remain large enough to be important for educational policy. Thus, small classes in early grades appear to have lasting benefits.
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