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What exactly does that mean?
It means that just putting guards in schools isn't going to really solve the gun violence problem. Or even the school shooting problem.
I'm convinced it all stems from a mixture of a few different things: 1) males, especially the young, kind of floundering in modern society, uncertain of what they're supposed to aspire to be, unable to dedicate themselves to excellence, too often disillusioned with overwhelmed mothers and absent fathers, 2) the instant gratification culture of social media, sensationalism, and internet infamy, 3) a country that is very, very bad at regulating weapons.
Your solution does not even come close to touching the root causes. After all, AR-15's and other semi-auto and fully-auto weapons have been around for ages. Since the 40's and beyond. Yet the first publicized school shootings were in the sixties, I believe, and we only continued to climb from there to reach the rate of mass shootings we see today, school or otherwise. These guys are using the same weapons that have been around for ages, so it's not like that's changed. It's young men who have changed. Or, rather, the lack of responsibility, expectations of achievement, and supervision in their lives