If you want to stop "school shootings" you have to understand the causes, so that you might target them and eliminate them. I do not understand them.
I think Tom Servo's early post rightly stated depression, sense of failure and rejection, disaffection, lack of self worth and a yearning for that morbid Warhol-esque moment of fame are all symptoms and possible drivers.
The use of guns and the choice of schools are also symptoms.
Whilst it may not reduce shootings, somehow breaking the connection between schools and the "glory" aspect the shooters seem to crave might at least make kids a less likely target.
Ultimately, school shootings make the news because they revolt us so. They are an attack on the very group in society that merits the greatest detachment from danger and harm: our children.
As one member pointed out (Tirod, I think) school shootings, as a cause of death, are relatively low on the scale of numbers.
It is on the scale of shock and outrage that they reign supreme.
Finding the answer will probably require digging deep and rewriting many aspects of modern society: this is something that goes against the contemporary desire for simple explanations and quick solutions and thus the bane of the "elected official".
Until people are willing to drop the slogans and simplistic proposals in preference for the actual issues, the problem will, IMHO, continue sadly.