NSCR-Schoolproject is the umbrella for a research program with four partial studies, aimed at enhancing insights into the development of delinquency and other problem behavior of adolescents, and the role of peer network formation among students, psycho-social development, and reactions from the school on problem behavior. The NSCR Schoolproject aimed to enhance insights into the complicated relations between delinquency and other problem behaviors, psycho-social development, peer networks, and school informal interventions. Data from teacher interviews. In this sub project we analyze intervention strategies of schools with regard to problem behavior of their students. Part of this was a small follow up study to analyze how individual teachers perceive problem behavior and how they implement school policies in practice.