Their are millions of biological parents in this country but very few of them are actually parenting their children.
To be sure, if you're not relying on government hand-outs, it's nearly impossible to maintain a decent standard of life without both parents being out in the work force. That's a big problem and it needs to be addressed.
When parents can't be there for the child when they need comforting, or have difficulty coping with a stressful situation or conflict, they learn you get attention by lashing out. It's not good attention but it is attention and in a world full of strangers it's the best they can hope for.
Sure there are exceptions, but for the most part a daycare raises children until they're old enough to go to school, then the government raises them after that. Schools don't really teach children as much as try to guide them on how to learn and in the absence of that ability a child will mostly become more antisocial and willing to lash out if they don't think anyone cares. Parental involvement seems like the best solution to insure they know someone cares.
If these young shooters had an attentive and caring parent they could turn to find another way to cope I doubt there would be as many of these events, so that should be the focus. Providing more time for parent/child interaction and seeking a resolution. If school started the mess, how can anyone expect them to resolve it?
P.S. I might be a little all over the place, but hopefully you'll know what I mean.