Since the Collaborative for Academic, Social, and Emotional Learning (CASEL) started working with state education agencies in 2003, the level of activity to advance social and emotional learning (SEL) has accelerated significantly, particularly in the past few years. State education leaders and policymakers are taking numerous steps to help districts and schools support students' social and emotional development and closely align these efforts with academic improvements. This report shares eight key insights and examples emerging from the work: (1) Since 2003, there has been growing momentum in state efforts to promote student social and emotional development, evidenced by an ever-increasing number of states that have developed policies and guidance to advance SEL; (2) Customizing SEL--each state is using an approach that works for its own districts and schools; (3) State education agency leadership is key; (4) Integration of SEL across state programs and policies is important to the ultimate success of these efforts; (5) Equity, cultural competence, and SEL are intertwined, and policymakers and educators must address them together to optimize student SEL generally and employability in particular; (6) Effective, customized messaging and communication are important to engage all the stakeholders; (7) Professional development is critical in advancing SEL, and states can play an important role in supporting districts and schools, using a variety of different approaches; and (8) A cross-state community of practice can be very powerful in advancing systemic SEL.