18. Boycott the NRA and start a new gun orgaization with responsible leadership.
That fixes that problem.
Next, build double-door (airlock) entrances for schools that use metal detectors to decide whether to trap entrants inside until they can be inspected. Bullet-proof Lexan plastic windows will reduce potential victims to one... the shooter. Implement fire-door style classroom doors that close and lock automatically if a panic button is hit anywhere in the school, and have safe rooms every 20 feet that children and teachers can run to and lock themselves inside, also with Lexan windows, so they can open the rooms to save others. One time expense that's a lot more effective than hiring a policeman.