Considering the political divide around this point as something that will not be resolved anytime soon, there should be a long term 'temporary' solution.
Schools should be fenced and gated with one or two armed guards depending on the size of the school.
In Israel every school and public kindergarten has an armed guard and it's been 30 years since a shooting incident in a school. Just the potential for such a terrible event is enough to ensure public support.
It's not perfect but usually guards are enough to deter potential troublemakers, sending them off to find an easier target.
OTOH most terrorists aren't as well equipped as American homegrown wackos.
In 30 years, every school in the West will have armed guards.
If there's a better argument for a parent to go out and buy an AR-15 than armed cops preventing unarmed civilians, intent on protecting their children, from entering an active shooter zone, I don't really know what is.
America was founded on "well if those in charge won't fix shit, we will", and those cops threatening parents with tazers deserve to have their badge taken away at a minimum, and personally, I think they oughta lose their balls, too. Cowardice at that level, where you're biting at those on your own side, in this sort of situation, deserves the harshest punishment.
God forbid I ever have a kid, and I've no desire to own a gun, but if I did, those Texan "law enforcement officials" would have given me all the motivation I'd need to go buy whatever was necessary to protect my family.