This report defines school refusal behavior as the refusal to attend school or difficulties going to school or remaining in school for the entire day, and sees school refusal as a significant problem that may occur in 8% of all school-aged children. It discusses difficulties of previous classification and assessment strategies for students who refuse to attend school. A proposed functional model for assessing and treating children and adolescents with school refusal behavior is outlined in which the focus is on why children refuse to attend school. This model hypothesizes that children refuse to attend school for negative reinforcement, such as avoiding stimuli within a school setting that provoke negative affectivity, and/or positive reinforcement, such as pursuing rewarding stimuli outside the school setting such as playing, being with friends, or parental attention. Preliminary data from 42 children with difficulties attending school, 42 mothers, and 29 fathers are presented which support the functional model. Included are reliability and validity data for the School Refusal Assessment Scale, an instrument designed to measure the function of school refusal behavior. A second report looks at whether the functional model can accurately predict the effectiveness of a specific, prescriptive, therapeutic strategy for a child with school refusal behavior. (NB)