This study was designed to assess the impact of providing teachers and principals with performance feedback on instructional practice, principal leadership, and student achievement. The teacher and principal performance feedback that was the focus of the study's intervention incorporated promising features of educator performance measures identified by recent research. The impact of the 2-year intervention was assessed through a school-level randomized experiment conducted in 127 elementary and middle schools from eight districts. The study found that providing educators with performance feedback had positive impacts on teachers' classroom practice, principal leadership, and student achievement in mathematics but not in reading.