School districts historically approached conflict-resolution from a zero-sum perspective: suspend students seen as disruptive and potentially harm them, or avoid suspensions and harm their classmates. Restorative practices (RP) -- focused on reparation and shared ownership of disciplinary justice -- are designed to avoid this trade-off by addressing undesirable behavior without imparting harm. This study examines Chicago Public Schools' adoption of RP. We identify decreased suspensions, improved school climate, and find no evidence of increased classroom disruption. We estimate a 19% decrease in arrests, including for violent offenses, with reduced arrests outside of school, providing evidence that RP substantively changed behavior. [Additional funding provided by the Becker Friedman Institute for Economics at the University of Chicago and the Hymen Milgrom Supporting Organization through the Successful Pathways from School to Work initiative of the University of Chicago.]