That’s a darned good idea. With entrance cameras, they’d see him coming with a duffel bag, and could be ready to drop him quickly.
It is kinda hard to get a gun out of a duffle bag, quickly, too.
You call good guys with guns to stop bad guys with guns - and they stop the bad guys by using guns. Folks need to cut out the middleman and do the stopping themselves - and schools need to allow their personnel to have the tools.