This meta-analysis assesses the effectiveness of volunteer tutoring programs for improving the academic skills of students enrolled in public schools Grades K-8 in the United States and further investigates for whom and under what conditions tutoring can be effective. The authors found 21 studies (with 28 different study cohorts in those studies) reporting on randomized field trials to guide them in assessing the effectiveness of volunteer tutoring programs. Overall, the authors found volunteer tutoring has a positive effect on student achievement. With respect to particular subskills, students who work with volunteer tutors are likely to earn higher scores on assessments related to letters and words, oral fluency, and writing as compared to their peers who are not tutored. (Contains 2 tables, 1 figure and 1 note.)