The notion of school disorder has captivated researchers and the public since well-publicized incidents of school violence have dominated the media. The article addresses a gap in the literature concerning school disorder by focusing on the relevant distinctions between different measures of school violence ranging from serious to minor and by examining institutional versus individual predictors of school disorder. Self-report survey data were gathered from 5,203 Philadelphia middle school students during 1994 through 1995. Measures focused on school climate variables such as clarity and fairness of rules; individual student characteristics such as age, sex, race, and dimensions of bonding; and two measures of school disorder: self-reported school offending and less serious school misconduct. Results of hierarchical linear modeling techniques revealed that schools varied significantly on both types of school disorder, with individual-level variables explaining a greater proportion of the more serious school Offending while school climate variables were more predictive of the less serious school Misconduct. As such, the author concludes that serious, school offending seems to have more to do with individual student characteristics than with school-level factors. The implications are that school security initiatives aimed at improving school climate may be effective only in reducing less serious misconduct, rather than serious offending behavior. A balanced approach to individual and school-level interventions is better suited to reducing school disorder. Tables, notes, references