Tutoring has emerged as an especially promising strategy for supporting students academically. This study synthesizes 33 articles on the implementation of tutoring, defined as one-to-one or small-group instruction in which a human tutor supports students grades K-12 in an academic subject, to better understand the facilitators and barriers to program success. We find that policies influenced tutoring implementation through the allocation of federal funding and stipulation of program design. Tutoring program launch has often been facilitated by strategic relationships between schools and external tutoring providers and strengthened by transparent assessments of program quality and effectiveness. Successful implementation hinged on the support of school leaders with the power to direct school funding, space, and time. Tutoring setting and schedule, recruitment and training, and curriculum influenced whether students are able to access quality tutoring and instruction. Ultimately, evidence suggests that tutoring was most meaningful when tutors fostered positive student-tutor relationships which they drew upon to target instruction toward students' strengths and needs.