Don't look at school shootings, they don't matter. What matters is how many, not by what means. Note that the most deadly such attack was with a truck, not a gun.

The data proves nothing about whether it works because it's a cultural problem far more than it is a means problem. They choose to go out in a blaze of infamy rather than be a nobody. They generally are planned long in advance, there's plenty of lethal things they can get their hands on.