Tutoring ranks among the most versatile and potentially transformative educational tools available. Dozens of randomized experiments have evaluated preK-12 tutoring programs, varying widely in approaches, contexts, and costs. This article presents results from a systematic review and meta-analysis of tutoring field experiments. We develop a framework for understanding variation in tutoring program impact and examine effect sizes (ESs) across a range of characteristics. We find that tutoring programs yield consistently substantial positive impacts on learning, with an overall pooled ES of 0.288 SD (SE = 0.029, p < 0.001). ESs tend to be largest for programs that use teachers or paraprofessionals as tutors, are held in earlier grades, occur at least 3 days per week, and are held during school.