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. This is the data from the longitudinal survey (3 waves) of the NSCR Schoolproject. This is one of the main data files for this study.