Law enforcement response issues aside, how hard would it be to fit these schools and school rooms with better secyrity systems? Doors with electronic locks, classrooms with one way steel doors that automatically lock from the inside, security cams and monitor systems over classroom doorways, security fencing around playgrounds, etc?
It would be expensive to refit all of these buildings and classrooms with real security doors, but we are already spending hundreds of millions to babysit a bunch of gangbangers with 60 level IQs for 12 years.
