This Wallace "Perspective" delves into what makes for a high-quality, voluntary summer learning program, one that provides children from disadvantaged communities with engaging academics as well as stimulating enrichment activities during the interval between the end of the school year and back-to-school time. Interest in these programs has grown in recent years, as educators and policymakers look for ways to close both the achievement and opportunity gaps between lower- and higher-income children. This "Perspective" summarizes takeaways from the National Summer Learning Project, a multi-year Wallace initiative to support the summer learning efforts of five school districts and their partner organizations--Boston; Dallas; Duval County (Jacksonville), Florida; Pittsburgh; and Rochester, New York. It draws on insights from a wide-ranging, multi-volume study of the initiative by the RAND Corporation, as well as interviews with the summer organizers and participants themselves, from district administrators and out-of-school-time providers to teachers, parents and children.