Create a new job in the military (or for military vets) to be armed guards at schools.

It is what the headline says it is: a job for Vets to defend America's youth. Depending on the size of the school the number of Vets on duty should vary. They should also get a gun safe with at least three different types of locks (key, combination, and keycard) to prevent anyone other than the Vet from opening the safe, and should be appropriately armed for any sort of gunmen that try to shoot at schools. With this, we create new jobs for Vets (who are better trained for these sorts of situations than regular police, excluding SWAT), defend schools from gunmen, and take some scrutiny off of the second amendment.