Analyzed data from a five-year followup of students in Tennessee's Student/Teacher Achievement Ratio (STAR) project, a four-year large-scale randomized examination of the effects of class size on academic achievement. Results suggest that class-size benefits persist for at least five years and remain large enough to be important to educational…

Although experimental results indicate that smaller classes promote higher achievement in early elementary school, the broader literature on class-size effects is inconclusive. This seeming contradiction raises questions about the generalizability of experimental evidence, an issue that this article addresses by examining the effects of class size…