The Early Intervention for Children at Risk for Developing Behavioral Problems (EICR) is a community-wide intervention model preventing and treating problem behavior and promoting social competence in children. The aim of the study was to test whether EICR would result in fewer incidences of problem behavior and improved learning climate in elementary schools in a Norwegian municipality. The municipality was divided in two, each section having equal chance of being assigned to the intervention condition. Participants were principals and school staff. One year after the initiation of EICR, the prevalence of student problem behavior was significantly lower, and student relations were significantly better for schools located in the intervention area than for schools located in the comparison area. The findings support further development, implementation and research on the EICR model.