Social robots are being adopted in PreK-12 schools around the world and have the potential to initiate far-reaching changes in education. Analysis from high-quality field studies is essential for educational researchers, administrators, and practitioners to make informed decisions about using these robots. We identified 23 studies between 2000 and 2020 that examined social robots in classroom settings. The 23 studies illustrated the feasibility of using social robots in natural school settings but revealed how difficult it was to obtain long-term, highly autonomous interaction between robots and children.The studies varied considerably on key conditions (e.g., length of deployment, the autonomy of robotic action, and length of interaction time). The studies did not demonstrate that social robots are more effective than human teachers (or even other forms of technology), and only occasionally explored important ethical and safety issues.