This review summarizes virtually all available evidence on the effectiveness of specific afterschool programs, based on a comprehensive literature search and review of studies published in 2000 or later. The review is motivated, in part, by a growing emphasis on using rigorous assessment of program impacts to inform decision-making in education and youth development programs. This review uses the Every Student Succeeds Act (ESSA) evidence framework to assess the evidence of afterschool program effectiveness. ESSA describes a tiered evidence framework of four levels, or tiers: Strong (Tier I), Moderate (Tier II), Promising (Tier III), and a fourth category that has been titled Demonstrates a Rationale (Tier IV) in September 2016 guidance from the U.S. Department of Education. In this review, the authors use ESSA's evidence requirements and the Department's guidance to identify afterschool programs that are judged to be supported by evidence at each tier. The authors also provide further definition for Tiers III and IV, which are described only generally in both ESSA and the guidance. Key findings include: (1) There is a substantial set of afterschool programs with evidence of effectiveness meeting ESSA Tiers I-III, including branded and unbranded programs; (2) Effective afterschool programs can be found at each grade level and within almost every program type; and (3) There are more afterschool program options for improving mathematics and reading/ELA achievement than for improving other outcomes. This report is organized into the following chapters: (1) Introduction; (2) How We Conducted the Review; (3) The Landscape of Afterschool Studies; (4) Evidence-Based Afterschool Programs under the Every Student Succeeds Act; and (5) Key Findings and Recommendations. [For the companion guide, "A Companion to Afterschool Programs: A Review of Evidence under the Every Student Succeeds Act. Afterschool Evidence Guide," see ED593606.]