The cross-sectional surveys and official crime statistics presented in Chapter 1 indicated that there were two main developmental trends in adolescent aggression and violence. The first, as surveys of nationally representative samples of middle and high school students showed, was that the middle school through early high school years, roughly ages 11 through 14, represented a peak time in which conflicts erupted into physical aggression, as well as for slight increases in the prevalence of more serious violence perpetration and victimization. Following early adolescence, and with some noteworthy exceptions (e.g., the stable prevalence rate for being shot), the prevalence of aggression and some forms of violence decline during the remainder of the high school years. This rise and fall of relatively common forms of aggression and violence was contrasted with a second trend. Homicide and arrests for seriously violent crimes show an escalation toward a peak at ages 18 and 19, before declining, or a relatively steady prevalence rate for the most serious self-reported violence. Explaining this bifurcated trend within the context of pre-adolescent and adolescent development is the main focus of the current exposition.

Understanding these two important trends in aggression and violence requires an appreciation of individual adolescent development and the social context of adolescence that triggers interpersonal violence. Moreover, it requires an understanding of both child and adolescent development, with special attention to subgroups of children and adolescents at greatest risk for the most serious violence; those who have veered off the mainstream developmental path.