There is an increased body of research indicating the importance of social -emotional learning (SEL) in schools. SEL is the processes of acquiring the skills to recognize and manage emotions, develop caring and concern for others, make responsible decisions, establish positive relationships, and handle challenging situations efectively. It is pro-moted through both direct instruction and the establishment of safe, caring, and support-ive learning environments in which all students feel valued, respected, and connected. In support of such arguments are studies linking SEL to a number of positive students’ outcomes, including beter academic achievement, social behavior, and emotional well-being. This chapter addresses how SEL, especially relationships as a critical component of SEL, contributes to school success and mental health especially among youth, with research evidence. Further, on the basis that we often do not feel eicacious in fostering SEL due to inadequate training and information, this chapter provides evidence-based practices to support healthy relationships and learning environments.