Playworks is a school-based program that places full-time coaches in low-income schools to organize games and activities during recess. The Robert Wood Johnson Foundation (RWJF) contracted with Mathematica Policy Research and its subcontractor, the John W. Gardner Center for Youth and Their Communities (JGC) at Stanford University, to conduct a rigorous evaluation of Playworks. Twenty-nine schools interested in implementing Playworks, across six cities in the United States, were randomly assigned to treatment and control groups during the 2010-2011 (cohort 1) or 2011-2012 (cohort 2) school year. Random assignment was conducted within matched groups of schools within each city. In total, there were 12 blocks of matched schools. For each block, one school was randomly assigned to the control group and the rest to the treatment group.