Developmental hyperactivity, organic factors, and temperamental deviance are addressed, and the prevalence of serious school misbehavior in low-track academic sections is reported. The small percentage of disruptive adolescents who present evidence of major psychiatric illness, particularly when coupled with poor impulse control, are shown to have a greater relative degree of behavioral deviance. Evidence that members of student gangs are far less successful in academic and school behavioral adjustment than nongang members is noted, and evidence that drug use by junior high and high school students is widespread is reported. Teaching styles that have been effective in improving classroom behavior are delineated, and the greater prevalence of serious school disruption and student victimization in secondary than in elementary school is described. Additionally, the effects of school size, structure, and atmosphere on school conduct are discussed, and patterns exhibited by parents of aggressive adolescents are identified. Evidence indicating that minor and moderate reductions in social disadvantage do not decrease school violence is reported, and regional differences in disruptive and delinquent school-related offenses are analyzed. Finally, the influence of racial tension on school violence is assessed, the availability of weapons in urban secondary schools is noted, and disruptions caused by unauthorized nonschool persons are described. Included are 100 references.