Might be a hot take, but when it comes to arming teachers, the Police were armed and gathering outside the school, but were unwilling, or at least slow to intervene in the shooting, to the extent that parents were taking about rushing the gunman. I don't actually think this is unreasonable of the Police, it's a job, we as a society can't expect someone who earns $70k a year to rush into a classroom to face down a loaded AR-15, despite their extensive training. Somehow we're supposed to expect teachers, with minimal training to do this?
Apparently we can't pass any new gun regulations.
Can't rely on the Police, despite events like this driving a massive militarization of our Police forces.
Can't rely on school security.
Not going to be able to rely on teachers with guns.
So I guess we just do nothing? Maybe more backpacks with armor plating?