Recently, nonmaternal center-based child care has been linked to problem behavior in young children (National Institute of Child Health and Human Development, 2003). In response, a comprehensive program to promote prosocial skills was evaluated in a classroom of 16 children between the ages of 3 and 5 years. Classroom observations were conducted during evocative situations to determine the likelihood of problem behavior (noncompliance, vocal or motor disruptions, aggression) and preschool life skills. A classwide teaching program was then implemented in a staggered manner across instruction following, functional communication, delay tolerance, and friendship skills. These four categories of preschool life skills, which included two to four related skills, were selected for classwide teaching because they were either identified by educators as important for early school success, have often been taught following functional assessments of more severe problem behavior, or both. Skills were taught on a classwide basis during typically scheduled activities (circle, free play, transitions, meals) via instructions, modeling, role play, and feedback. A multiple probe design showed that the program resulted in an 74% reduction in problem behavior and a more than four-fold increase in preschool life skills. Similar beneficial effects of the program were evident in questionnaire data gathered prior to and at the close of the evaluation. Finally, the teachers who implemented the program reported overall high levels of satisfaction with the classwide teaching program, the target skills, and the results. Implications for the design of early childhood experiences for preempting the development of serious problem behavior are discussed.