A new examination of 123 studies spanning four decades – from 1960 to 2000 – finds that preschool confers what one co-author calls “lasting and substantial” benefits that don’t fade after third grade and that effectively help close the achievement gap.

The study “Meta-Analysis of the Effects of Early Education Interventions on Cognitive and Social Development,” published by the Teachers College Record at Columbia University, concludes that children who entered kindergarten after attending preschool showed significant positive effects in their cognitive and social-emotional development, as well as their progress in school, with the greatest benefits evident in their cognitive outcomes. Co-author W. Steven Barnett, co-director of the National Institute for Early Education Research at Rutgers University, summarizes the report’s findings in a 2½-minute video.

“The central message from our study is that looking across the entire research literature over decades – 123 different studies – preschool has substantial impact,” Barnett says. “If we focus on rigorous studies, the immediate impact on cognitive development is to close about 70% of the achievement gap. If we then ask, ‘After third grade how much of the achievement gap is closed by preschool education?’ About a third. Now that’s substantial.

“Our study also finds that design of a preschool educational program matters. Intentional teaching and individualization, two things that every preschool teacher knows or should know are important, increase the size of the effects substantially. I think the key message for policymakers is this really is the last nail in the coffin on the idea that preschool education’s effects fade out after third grade. If you look at all the research – you don’t cherry pick your studies – they don’t. They’re lasting and substantial.”