The study reviewed in this paper examined whether "Playworks," a program that utilizes full-time coaches to provide structured play opportunities during recess and class time, reduces the number of disciplinary referrals in low-income elementary schools. Study authors randomly assigned 25 schools in five US cities to either a "Playworks" group during the 2010-11 school year or to a comparison group that did not use the "Playworks" program but was eligible to implement the program during the following year. To estimate the effect of "Playworks" on disciplinary referrals, study authors compared the number of disciplinary referrals reported by school principals over the course of one week during the spring of 2011 in 12 intervention schools to the number of reported referrals in 10 comparison schools. The study did not find any statistically significant differences between the "Playworks" schools and comparison schools in the number of disciplinary referrals. The research described in this report meets the What Works Clearinghouse (WWC) evidence standards without reservations. Appended are: (1) Study details; (2) Outcome measures for the external behavior domain; (3) Study findings for each domain; and (4) Supplemental findings by domain. A glossary of terms is included. (Contains 4 endnotes.)