My point is the guy who wants the gun will still get it…criminals have illegal guns all the time. So if someone wanted to do it they would have a gun and you would just sit and watch as you mowed down.
Actual criminals don't do this shit. They use guns for proper crimes like robery, gang violence, drug trade etc.
I live in a country where only criminals have guns and I feel a lot safer. It's Jealous Joe and Incel Mike down the street, you need to be concerned about. They never commited a crime on their lives, and would never get past the necessary hurdles to find an illegal gun. Those are the ones I would actually need to be afraid of if I lived in America.
Guns are useless for defence anyway. It's all Hollywood crap. Initiative and willingness is what decides the outcome of shootouts. It.won't matter how armed the security guy is. He'll just be shot from the back instead. These guys chose schools because it hurts society more, not because it's easier.
Your only reasonable point is that the ban wouldn't stop shootings. Not overnight. It's largest benefit would probably be a slow change of culture. Less leople learning to shoot, less people in gun ranges, less guns in TV or youtube. 30 years from now they would be seen by the majority of the population as a stupid thing of the past.