Urban school districts will face a number of new and unprecedented challenges in the 2020-2021 school year. In addition to safely reopening schools, planning for the likelihood of future rolling school closures, redesigning instructional delivery models, and effectively addressing unfinished learning and learning losses among students, schools will need to address the significant social and emotional toll that the crisis has taken on children and adults alike. Districts will need to create learning environments that make students and their teachers feel safe and socially and emotionally supported as they return to school. To meet these needs, significant restructuring and reallocation of resources will be necessary, as social-emotional learning and mental health have traditionally been blindspots for many school systems. In general, addressing the mental health needs of students is not universally understood or embraced as the central work of schools or districts. Efforts in this area have been relegated to siloed mental health, social-emotional learning (SEL), and student services departments, working without sufficient resources, coordination, or access. But as anyone who works with students can attest, attending to the mental health and social-emotional wellbeing of students is not an external consideration--it is a necessary condition for learning. In the context of COVID-19, it is going to become an even more pressing consideration in how schools educate and support students, as districts will need to prioritize the emotional wellbeing of students as they re-engage them in academic content. This guide presents a set of overarching principles and strategies to address the social-emotional and mental health needs of both students and adults. It then highlights some of the key efforts being undertaken and resources being offered in a set of districts that we have identified as leaders in the field: Broward County Public Schools (FL), the Cleveland Metropolitan School District (OH), the Los Angeles Unified School District (CA), and Tulsa Public Schools (OK). The end of the guide provides a list of academic and district experts in the field of social-emotional learning and behavior and mental health.