yes, but that's still irresponsible. 12 is when middle schoolers become emo and puberty and etc cetera. And sometimes this can lead to kids doing stuff like drug dealing. (This actually happened at my school once, the police showed up and everything). So combine that with most middle schoolers being twisted little piles of sh*t AND deadly firearms, and you've got yourself a situation way more deadly than school shootings. Unpopular teachers would have their lives on the line, crime would be common outside of school, poorer kids would have a huge disadvantage in you're whole idea as they can't afford guns and unpopular kids would now find themselves facing to rich bullies with shotguns and m16s, ready to threaten and blackmail them however they like.
Is that your idea of safety?