I’d suggest placing retired cops and military men in the schools with AR-15’s or something similar. Pay them a small stipend.
Nah. Shotguns. Avoid overpenetration, accidentally killing Mrs. McGillicuddy in her clapboard house 1-3/4's miles away.
Something like that happened in the 1992 L.A. riots. The Korean shopkeepers cranking rounds at the rioting black mob nailed a Hispana coming home from the grocery on foot. She was something near two miles from the riot zone [TIME reported] when she stopped a big-bore pistol bullet with her forehead. She dropped dead on the spot.
Then there was the Philadelphia woman who had a late-night visitor in the form of a .223-cal. round come through her apartment wall just above her head, from a LE/SWAT/SpecOps live-fire exercise in a vacant high-rise a mile or so away. A round got away and came to see her. Interrupted her bedtime reading.