Frankly, twins, my elementary and junior high school had plenty of violence, in the form of at least one or two fist fights any given week. A lot of the guys, from around fifth grade on, had BB gun wars when not at school. But my area did not have school shootings or stabbings.
I sometimes wonder if there is not some advantage in letting kids figure out early that violence hurts.
Kind of parallels how modern parents, in keeping their kids away from "harmful" things like dirt and critters, seem to have stifled their kids' immune systems. Farm kids tend to have fewer allergies...