The reason you’ll never get approval to arm some of the teachers is twofold:
First, you’re dealing with a true and deep phobia. Leftists FEAR the object, the gun, irrationally.
Second: leftists want TOTAL CONFISCATION of all privately-held weapons, and can not admit to them being an effective deterrent to a mad shooter. Secretly, they fear they can not ram the full socialist agenda down the country’s throat as long as any credible ultimate means of resistance still exists.