I'll take experience of age and training over unfocused youthful aggression any day. Your refusal to accept the deterrent effect of increased risk of effective resistance is irrational. It takes very little consistent training to be reasonably proficient, and it wouldn't just be the teachers. Janitors, the principal, clerical staff, the lunch ladies, librarians, everyone has the natural right to self-defense with the most effective technology they wish to use. Disarmament is trespass.
If the availability of weapons is the root cause of violence, why is it only manifesting in mass shootings at "gun-free zones" while violent crime rates overall plummeted, and most violence is associated with black market drug trade and economic segregation? Do you know what else started spiking in the 1990s? Drug prescriptions for kids. Antidepressants, ADHD medication, and other psych meds meant to help them cope with the antisocial school structure imposed upon them. You look at the guns as the root problem. I suggest we look at the schools themselves.
Your answer of government violence is too simplistic. How many people are you willing to see murdered to impose your dystopian ideal? We already see brutal police abuse against people who are making, selling, and consuming drugs in spite of prohibition. Alcohol prohibition created violent gangs in the 1920s. Government violence is not the answer, it is usually in fact the root problem of societal ills.