Ten years ago, Child Development published the pivotal meta-analysis by Durlak and colleagues (2011) examining the state of the evidence for universal school-based (USB) social and emotional learning (SEL) interventions that was available through December 31, 2007. Durlak et al.’s positive findings have been followed by substantial changes in educational practice and policy; and the paper remains the most frequently cited justification for investments in SEL, even though the review only synthesizes studies through the end of 2007. This study provides an update of the evidence available for USB SEL programs from January 1, 2008 through December 31, 2020. We begin by describing significant developments in what aspects of SEL content and implementation make a difference in which outcomes and who benefits (or not) from USB SEL interventions. This review is addressing the need for an update of the current state of evidence for USB SEL interventions among students in grades K-12. We embrace the evolution of the field of SEL by using a comprehensive and inclusive definition of USB SEL and include hypothesized features of USB SEL implementation identified in the contemporary literature to explicate the associated evidence for USB SEL interventions on outcomes. We welcome you to read our codebook and supplemental material on this page to learn more about our definition and framing. This systematic review and meta-analysis of the evidence for USB SEL is following the contemporary PRISMA guidelines, adhering to a predetermined, peer-reviewed protocol to strengthen transparency through pre-registration. Upon completion, we will share the analytic files on Open Science Framework (OSF) alongside the data set on GITHUB and instructions and code for analyses to support reproducibility and training opportunities in the field of SEL. This page provides more information on this project and will be updated periodically. Please direct inquiries to christina.cipriano@yale.edu