What are schools doing to prevent delinquency and promote school safety? This NIJ Research in Brief (NCJ 205005) presents findings from a national survey of elementary, middle, and secondary schools. Problem behavior is widespread and most common in urban areas and middle schools. Schools have adopted a large and diverse array of activities, curricular programs, and security measures, but many of these are unproven or poorly implemented. Key characteristics of successful programs and how schools can improve program quality and implementation are identified.