Given the substantial and oftentimes irreversible human loss resulting from aggressive acts, the need for systematic, treatment-linked assessment of aggression in school-aged children and youth cannot be overstated. Based upon recent research, the authors provide a broadly framed model for the functional analysis of aggression in school-age children and youth. Our model incorporates multi-modal data collection and data triangulation to generate credible hypotheses regarding the function(s) of aggression. Three primary data sources—record review and interviews, naturalistic observation, and analogue assessment—form the cornerstone of the model. Key features of our approach to the assessment of aggression include operational definition(s) of target behavior(s), examination of the environmental context(s) of aggression, and discovery of the function(s) of aggressive behaviors for the individual. Samples of several specific, ready-to-use data collection instruments and a basic description of the assessment procedure are presented. The assessment process assumes that a team of individuals participates in data collection, data analysis, and hypothesis generation
