Following a surge of research showing the importance of social and emotional competence for children's academic and social success (e.g., Durlak, Weissberg, Dymnicki, Taylor & Schellinger, 2011; Sklad, Diekstra, Ritter, Ben & Gravesteijn, 2012), education policymakers across the country have made efforts to incorporate social and emotional learning (SEL) into state standards of learning. Today virtually all states have comprehensive, free-standing SEL standards at the preschool level, and at the K-12 level most states have made at least some efforts to integrate social and emotional competencies in other sets of academic standards, such as Health, Social Studies, or English Language Arts (Dusenbury et al., in press). However, only a few states have comprehensive, free-standing SEL standards at the K-12 level. Further, SEL standards vary substantially from state to state both in terms of quality and inclusiveness. Most striking of all is the lack of alignment between birth to preschool standards and K-12 standards in how SEL is defined and emphasized. In this brief report, the authors review the importance of SEL for children's early and sustained success. They also discuss key characteristics of high-quality SEL standards and the benefits of preschool through high school standards alignment. Finally, they review examples of two sets of well-aligned standards and make recommendations for the development and implementation of well-aligned, high-quality state standards for SEL preschool through high school.