Abstract
The aims of this study were to assess the longitudinal trajectories of externalizing problem behavior during middle childhood among typically developing children and to examine subgroup differences in the effectiveness of the School-Wide Positive Behavior Support (SWPBS) model, called N-PALS in Norway. Participants were approximately 3000 students, and behavioral assessments were performed by class head teachers at four time points from the 4th or 5th grade through the 7th grade. Using a combination of latent class growth analyses (LCGA) and growth mixture modeling (GMM), four distinct trajectory classes were identified, i.e., persistent low (84.4%), persistent high (2.5%), decreasing (7.9%), and increasing (5.3%). An indication of a significant positive effect of the N-PALS model was found for students with a persistently high-risk trajectory. The current study adds to the evidence that this school-wide prevention model can moderate the development of externalizing behavior problems among children and youth.