Behavior problems are often observed in classrooms. The age at which problems appears is increasingly younger, and there are no interventions that ensure a reduction in such behavior problems among school age children. Research and previous evidence show the importance of social competence in this kind of prevention. Working with preschool and primary students must be the main objective, because social competence is a protective factor against behavior problems. In response to these social and educational problems, American and European countries have begun to include universal prevention programs in their curriculum, the ensure the learning of social competence at school. As an example, the pioneering program "Aprender a Convivir" [Learn to Live Together] can be considered a preventive intervention that encourages the innovative and optimal development of prosocial behavior in three- to seven year-old children. Its main contents are: rules, feelings and emotions, empathy, communication skills, interpersonal skills, assertiveness and problem solving skills. The framework focuses on increasing social competence and decreasing behavior problems, with the long term results of preventing antisocial behavior. The present contribution aims to first show the importance of working on social competence at school, and second, to present the "Aprender a Convivir" program. This program has been implemented in cities of Spain (Granada, Zaragoza), and in other Spanish-speaking countries (Bolivia, Dominican Republic), showing significant differences in the growth of social competence and the reduction of behavior problems.