Plenty of students brought knives to my blue-collar midwestern high-school only twenty years ago and I can't recall a single knife-fight, stabbing, or even anyone being threatened with a knife.
In upstate New York (of all places), we used to bring guns to school and store them in our lockers so we could go hunting after school. Use them against teachers or our fellow students? The thought NEVER crossed our minds. Of course, we were taught the difference between right and wrong back then, and we were steeped in a system of morals that included a righteous FEAR of G-d. You KNEW He was watching your every move, and you behaved accordingly. You also knew better than to anger your parents, who treated/disciplined you like CHILDREN, instead of close friends. (Oh...do I want Mexifornia? No. But isn't it too late?)