The Enduring Effects of Small Classes

The purpose of this investigation was to extend our knowledge of the effects of small classes in the primary grades on pupils' academic achievement. Three questions were addressed that have not been answered in previous research: (1) How large are the effects of small classes relative to the number of years students participate in those classes? (2) How much does any participation in small classes in K-3 affect performance in later grades when all classes are full-size? (3) How much does the duration of participation in small classes in K-3 affect the magnitude of the benefits in later grades (4, 6, and 8)? Rationales for expecting the continuing impacts of small classes were derived in the context of other educational interventions (for example, Head Start, Perry Preschool Project). The questions were answered using data from Tennessee's Project STAR, a statewide controlled experiment in which pupils were assigned at random to small classes, full-size classes, or classes with a full-time teaching assistant. Hierarchical linear models (HLMs) were employed because of the multilevel nature of the data; the magnitude of the small-class effect was expressed on several scales including "months of schooling." The results for question (1) indicate that both the year in which a student first enters a small class and the number of years (s)he participates in a small class are important mediators of the benefits gained. The results for questions (2) and (3) indicate that starting early and continuing in small classes for at least three years are necessary to assure long-term carryover effects. Few immediate effects of participation in a class with a full-time teacher aide, and no long-term benefits, were found. The results are discussed in terms of implications for class-size reduction initiatives and further research questions.