Evidence-based social and emotional learning (SEL) programs, when implemented effectively, lead to measurable and potentially long-lasting improvements in many areas of children's lives. In the short term, SEL programs can enhance children's confidence in themselves; increase their engagement in school, along with their test scores and grades; and reduce conduct problems while promoting desirable behaviors. In the long term, children with greater social emotional competence are more likely to be ready for college, succeed in their careers, have positive relationships and better mental health, and become engaged citizens. Those benefits make SEL programs an ideal foundation for a public health approach to education--that is, an approach that seeks to improve the general population's wellbeing. In this article, Mark Greenberg, Celene Domitrovich, Roger Weissberg, and Joseph Durlak argue that SEL can support a public health approach to education for three reasons. First, schools are ideal sites for interventions with children. Second, school-based SEL programs can improve students' competence, enhance their academic achievement, and make them less likely to experience future behavioral and emotional problems. Third, evidence-based SEL interventions in all schools--that is, "universal interventions"--could substantially affect public health. The authors begin by defining social and emotional learning and summarizing research that shows why SEL is important for positive outcomes, both while students are in school and as they grow into adults. Then they describe what a public health approach to education would involve. In doing so, they present the "prevention paradox"--"a large number of people exposed to a small risk may generate many more cases [of an undesirable outcome] than a small number exposed to a high risk"--to explain why universal approaches that target an entire population are essential. Finally, they outline an effective, school-based public health approach to SEL that would maximize positive outcomes for our nation's children.