The "Faustlos"1 curriculum, an adaptation of the American Second Step program, for the prevention of aggressive behaviors of elementary school children was evaluated in a 3-year control group study (30 classes served as an experimental group, 14 classes as a control group). The results show significant changes in the emotional competences and prosocial developments of children aged 6-9 years. Children who participated in the "Faustlos" lessons showed significantly reduced anxiety and internalizing behaviors compared with the control group. The parents' ratings of their children's behavior (according to the Child Behavior Checklist) provided clear evidence of improved social behavior outside the school environment.