Where Does School Violence Come From?
There are two core assumptions upon which most experts on the subject of school violence agree: 1) Violence is largely a learned behavior and 2) It enters schools from the streets and homes of the communities they serve.
However, the findings of a highly regarded Canadian study suggest that physical aggression may be an inherent behavior that is, in most children, effectively discouraged as they mature. The National Longitudinal Survey of Children and Youth (NLSCY) tracked maternal reports of levels of physical aggression in their children from infancy. It found that the most physically aggressive period in a child’s maturation to age 12 is 24 months—a finding likely to be heartily seconded by any parent or older sibling who has lived through the “terrible twos.”
From that point, with two lesser spikes at 36 and 42 months, the incidence of violent aggression declines throughout childhood.  The obvious implication is that physical aggressiveness isn’t taught in the home and on the street, but that the child’s environment encourages—or at least fails to discourage—its continuation.
Advocates of either view, of course, will argue that intervention to discourage physical aggressiveness should start at an early age. And either theory is consistent with the belief that violence that begins in childhood is more serious and persistent than violence that begins in adolescence.
Indeed, the trajectory of physical aggression reported in the NLSCY showed no adolescent spike in violent behavior. What does increase as the child matures is the level of indirect aggression—rumor-mongering, exclusion from groups and social events, spreading slanders—which is more commonly associated with girls than boys.
That suggests that physical aggression self-limits in most youngsters because it increasingly fails to achieve its purpose and often gets its practitioner hurt or in trouble, while indirect aggression is subtle enough to proceed beneath adult radar and hurtful enough to reward its user. Indeed, the popular literature on the subject, (e.g., Rosalind Wiseman’s Queen Bees and Wannabees) portrays a “girl world” alive with a chilling and subtle cruelty worthy of the venomous aristocracy of Louis XIV’s Versailles. As one expert observed, “It appears that girls don’t get a copy of the rules for fighting fair.” 
All authorities agree that adolescent males also engage in indirect aggression, mostly directed at disparaging a peer’s sexuality or physical prowess, or telling tales, true or false, about their own dalliances—thus besmirching the reputation of the girl. But it would appear that most would be well advised never to pit their skills at indirect aggression against those of an accomplished eighth grade girl.
To the degree that adolescent-onset violence does exist, there are suggestions in the literature that it is attributable to the shift in focus from the family to peers that occurs in adolescence. A plausible case can be made for attributing at least a significant amount of teen-onset violence to the influence of delinquent peers on a relatively non-violent adolescent, who subsequently rejects that influence and returns to a low-violence pattern of behavior. This would account for the relatively low levels of violence attributed to those identified as teen-onset participants.
If those who completely discount the existence of true adolescent onset aggression are correct, what may be misread as a physical aggression spike may be the increased visibility of such behavior stemming from the greater physical power, mobility and access to weapons that occurs in adolescence. The inhibition-lowering effects of drugs and alcohol also may produce a more intense—and therefore noticeable—level of violent aggression. Even the NLSCY identifies a constant 3.5 percent of youngsters who are physically aggressive at every age. 
Regardless of the theory applied to explain its origins, it is generally accepted that the violence in schools enters with the students from the neighborhoods the school serves. As visible and tragic as events like the Columbine shootings are, the vast majority of student violence is still what it always was—fistfights, bullying and shoving matches. 
 Quoted in Tremblay, R;, The Origins of Youth Violence, in Isuma: The Canadian Journal of Policy Research, Vol. 1, No. 2, Autumn, 2000, available at http://www.isuma.net/v01n02/index_e.shtml; accessed 30 August 2004
 Persephanie Silverthorn, Ph.D., University of New Orleans Applied Development Program, unpublished video interview, 13 August , 2004.
 The Origins of Youth Violence, Figure 1, p 20.
 Schwartz, W; Reducing School Violence; ERIC Clearinghouse on Urban Education, p.1., 1996, available at http://www.ericfacility.net/databases/ERIC_Digests/ed410321.html; accessed 8 August 2004