Many programs to prevent aggressive behaviours have been implemented at German schools. One such program is "Faustlos," a German adaptation of Second Step. This study investigated the social validity of the Faustlos curriculum in a sample of German fourth graders. Social validity refers to the level of acceptance associated with a prevention program. In our study 117 children were asked to report their opinions about Faustlos. The methods that were used throughout the program were differentially valued by the children. Moreover, results indicate that the children reported different situations in which they used and valued contents of the program. The results revealed three groups of children. Some children found the program useful, other children attributed usefulness to it, but based on theoretical knowledge and the third group reported no perceived usefulness. Findings will be discussed with regard to the further development of aggression prevention programs.