Having a cop in the school, who doesn’t run away, is effective.
Oakland tech/schools put County sheriffs in the school halls way back 40 years ago. Nuthin much happened after that.
Sometimes very educated people are the stupidest people. We`ve a cat who won`t put his paw back on a hot stove. My cat is smarter than most teachers are. Coyotes used to come near the porch but a couple warning shots and they never come back. Coyotes are smarter than teachers are.