Universal, school-based programs, intended to prevent violent behavior, have been used at all grade levels from pre-kindergarten through high school. These programs may be targeted to schools in a high-risk area-defined by low socioeconomic status or high crime rate-and to selected grades as well. All children in those grades receive the programs in their own classrooms, not in special pull-out sessions. According to the criteria of the systematic review methods developed for the Guide to Community Preventive Services (Community Guide), there is strong evidence that universal, school-based programs decrease rates of violence among school-aged children and youth. Program effects were consistent at all grade levels. An independent, recently updated meta-analysis of school-based programs confirms and supplements the Community Guide findings.