School shootings are rare, but highly publicized. Parents are in the lead. Barring a child being locked in a cage in the basement, used as a human ashtray or paraded around in Vegas showgirl outfits , a kid needs to be mentally disturbed to get up one morning, don fatigues and whack his algebra class.
Parents can pay attention to their kids.
They can nip problems in the bud. Everyone has thought of committing murder. Regardless of your reasoning, you do not pick up a gun and take over Red Lobster. You think about your actions. Most of us have enough sense and sanity to fantasize about, but not act on, our homicidal impulses.