Why? Many of the kids who've shot and killed classmates at school came from two-parent homes. Kip Kinkel even killed his two parents first, before heading off to shoot up the school.
When you hear about a kid shooting another kid, single parent households appear most often (by my observations).
You may be able to cite a few cases of kids killing at school (very rare), but every other "child" violence statistic goes the other way. Most of them are inner-city kids with a single parent in the household, and a marginal parent, at that.
The boy who killed a 6 year-old girl in Flint, Michigan had taken his drug-dealing cousin's pimp gun while his single mother was riding the bus to her token "workfare" job.
He was raised in a nice house, too, by politically correct parents. Years ago, it was just shacks up the Booth Kelly road and we kids all had guns and would hunt in that area after school. I learned to dance the bop in that cafeteria where he let fly. We hear he used to have fun blowing up cows before this happened, and the parents would wring their hands. Maybe there was a hint he was NKR, (not quite right as we used to say.)
Never a problem with us kids and guns. We all had 'em. Plenty of fist fights, though.