The purpose of the report series is to summarize the benefits of social and emotional learning (SEL) in early childhood, and identify the characteristics of SEL interventions that are effective in school contexts. Responding to a need expressed by the Early Childhood Education Research Alliance, the research team conducted a systematic review and synthesis of recent research reviews and meta-analyses on the topic of SEL. The review identified effective SEL programs, strategies, and implementation practices. These effective components include aspects of program design, teacher training and technical assistance, and integration of SEL with existing structures.