Tyler W. Watts

High-quality preschool programs are heralded as an effective policy tool to promote the development and life-long wellbeing of children from low-income families. Yet evaluations of recent preschool programs produce puzzling findings, including negative impacts, and divergent, weaker results than were shown in demonstration programs implemented in the 1960s and 70s. We provide potential explanations for why modern evaluations of preschool programs have produced less positive and more mixed results, focusing on changes in counterfactual conditions and preschool instructional practices. We also address popular explanations such as subsequent low-quality schooling experiences that, we argue, do not appear to account for weakening program effectiveness. The field must take seriously the smaller positive, null, and negative impacts from modern programs and strive to understand why effects vary and how to boost program effectiveness through rigorous, longitudinal research.

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Researchers and policymakers aspire for educational interventions to change children’s long-run developmental trajectories. However, intervention impacts on cognitive and achievement measures commonly fade over time. Less is known, although much is theorized, about socialemotional skill persistence. The current meta-analysis investigated whether intervention impacts on social-emotional skills demonstrated greater persistence than impacts on cognitive skills. We drew studies from eight pre-existing meta-analyses, generating a sample of 86 educational RCTs targeting children from infancy through adolescence, together involving 56,662 participants and 450 outcomes measured at post-test and at least one follow-up. Relying on a meta-regression approach for modeling persistence rates, we tested the extent to which post-test impact magnitudes predicted follow-up impact magnitudes. We found that post-test impacts were equally predictive of follow-up impacts for cognitive and social-emotional skills at 6- to 12- months follow-up, indicating similar conditional persistence rates across skill types. At 1- to 2- years follow-up, rates were lower and, if anything, cognitive skills showed greater conditional persistence than social-emotional skills. A small positive follow-up effect was observed, on average, beyond what was directly predicted by the post-test impact, indicating that interventions may have long-term effects that are not fully mediated by post-test effects. This pattern of results implied that smaller post-test impacts produced more persistent effects than larger post-test impacts, and social-emotional skill impacts were smaller, on average, than cognitive skill impacts. Considered as a whole, intervention impacts on both social-emotional and cognitive skills demonstrated fadeout, especially for interventions that produced larger initial effects. Implications for theory and future directions are discussed.

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