Social and emotional learning (SEL) involves the processes through which children and adults acquire and effectively apply the knowledge, attitudes, and skills necessary to understand and manage emotions, set and achieve positive goals, feel and show empathy for others, establish and maintain positive relationships, and make responsible decisions. Effective SEL programming begins in preschool and continues through high school. The Collaborative for Academic, Social, and Emotional Learning (CASEL) strives to advance SEL science, evidence-based practice, and policy. In an ideal world, CASEL would see every school in the nation providing evidence-based SEL programming to all students in preschool through high school. This guide provides a systematic framework for evaluating the quality of classroom-based SEL programs. It uses this framework to rate and identify well-designed, evidence-based SEL programs with potential for broad dissemination to schools across the United States. The primary goal of the Guide is to give educators information for selecting and implementing SEL programs in their districts and schools. It also documents the significant advances the SEL field has made in the past decade, establishes new and more rigorous standards for SEL program adoption, and provides suggestions for next steps for SEL research and practice.