This report from the Learning Policy Institute reviews the findings from 12 meta-analyses of school-based social and emotional learning (SEL) programs. Across these studies, there is a consistent, reliable effect of tested, evidence-based SEL programs on students’ social, emotional, behavioral, and academic outcomes in PreK–12th grade, including the development of social-emotional skills, improved academic engagement and performance, growth of positive social behaviors, and lower rates of behavior problems and psychological distress. These findings are applicable across gender, ethnicity and race, income, and other demographic variables.