The purpose of this report is two-fold: first, to provide an authoritative and critical overview of the current evidence regarding what is currently known about effective social and emotional learning (SEL) and in doing so, second, to examine common strategies and practices typically deployed in evidence-based SEL programmes in detail. The ultimate goal of this report is to identify "essential ingredients" (Aber, Brown, Jones, Berg, & Torrente, 2011, p. 218) within SEL provision to help inform effective strategies for teachers and other school staff. Evidence suggests that SEL is important, that it can be taught effectively, but that positive outcomes are dependent on a number of factors we are as yet to fully understand. Thus, the purpose of the current study was to identify the areas of greatest promise in informing schools' practice in relation to SEL. [For the related guidance report, see ED612290. For the related survey results, see ED612309.]