Umm… All of the recent school shootings were done with AR-15s. A teacher with a pistol is not going to be effective against an AR-15 as a pistol is not accurate to more than perhaps 5 meters. An AR-15 can easily kill at several hundred meters and an fire faster. Plus as soon as first response teams show up anyone in the school is a shooter and will be shot. I have mixed feelings about guns – I have known hunters who keep their guns locked up and only use them to hunt or a pistol to shoot animals (coons) close to the house. Sadly we simply have too many guns. Besides, no person with an AR-15, even fully auto, will be swatted like a fly by any decent military force. You would not stand a chance against a tank or an Apache helicopter or a squad in body armor.
I find it impossible to tell truth from false in the news gave up on TV after I threatened to throw something at it.