This evidence guide provides detailed research summaries on the effectiveness of specific afterschool programs for improving outcomes for students in grades K-12. The purpose of the guide is to present information that education agencies, afterschool providers, and others can use as they make decisions about afterschool programming. The guide is a companion to "Afterschool Programs: A Review of Evidence Under the Every Student Succeeds Act." The review is based on a comprehensive, systematic literature search for studies published between 2000-17 of the effectiveness of afterschool programs. Prior to this review, the full extent of evidence-building about afterschool programs was not known. This guide demonstrates that, since 2000, there have been many rigorous studies of the effectiveness of afterschool programs. This guide also provides information to use in decision-making about afterschool programming. This guide includes several types of evidence summaries: (1) Summaries of evidence for afterschool programs; (2) Brief summaries of the effectiveness of school-sponsored extracurricular programs; (3) Brief summaries of studies that meet a lower research quality standard; (4) Brief summaries of studies with insufficient information to assign an Every Student Succeeds Act (ESSA) tier; and (5) Brief summaries of studies of year-round out-of-school time programs. [For "Afterschool Programs: A Review of Evidence Under the Every Student Succeeds Act," see ED593600.]