Missing the point..
You're never going to be able to eliminate guns in the US. There are just too many in circulation. That said, when I was a kid, every boy child carried a pocket knife, and a lot of us had pellet guns and .22 rifles, and had families with shotguns and other arms. It never would have occurred to me to take one to school unless it was for show and tell, which probably would have actually been allowed if you cleared it with the teacher first. Or to use my pocketknife to stab someone. There were fistfights and bullying (which is not okay), but no one really considered actually killing their classmates. There weren't any mass shootings that I can recall before Columbine.
What changed in these decades? Were mass shootings just a meme, an idea whose time had come? Did the first one somehow make it "okay" for others to do the same? I don't know. One thing I do know is that our sanitized, politically-correct society allows resentment and anger to fester and build without a safety valve, and parenting skills are at an all-time low. And I believe that information being freely available is a wonderful thing, but I would have to admit that letting your kids view uncensored violence and destruction with no supervision does desensitize them. We also seem to think that kids are equal to adults and responsible for their own actions in the same way, while they are often still way too immature to realize the consequences of their actions or deal with heady emotions that they're feeling for the first time.
So what is the answer? I don't know. Banning everything in life that can be misused is not it though. This is the equivalent of putting your hands over your ears and singing "LaLaLaLa" to tune out something you don't want to hear. And arming teachers is ridiculous. If there is any solution IMHO, it is giving kids more education than what they get in Algebra class. Kids need to be raised to value their own lives and that of others, and when warning signs present themselves, the answer isn't to lock them up forever, but to work with them to salvage their troubled psyches before they become truly lost.