Methodology: The High/Scope Perry Preschool Study examines the lives of 123 African Americans born in poverty and at high risk of failing in school (Schweinhart, Barnes, & Weikart, 1993). At ages 3 and 4, we randomly divided these individuals into a group who received a high-quality preschool program and a group who received no preschool program. We collected data on both groups annually from ages 3 through 11 and at ages 14, 15, 19, 27, and, recently, 39-41. The study has had little attrition, with a median across all measures of only 5% of cases missing.After each phase of data collection, we analyzed the data and wrote reports of the study. This study demonstrates the power of an experimentally designed longitudinal study to reveal program effects, even decades after the program.
Existing research and our understanding of child development strongly suggest that the right kinds of early environmental enrichment should make a long-term difference for children who are born into impoverished environments. The findings presented in the chart below are impressive, but I don't have time to dig into the article, so feel free to discuss design flaws, confounds and anything else you see.