Guns in the classroom are a non-starter..

Unless someone can come up with a way to pay for implementing (pay for it) across the country it is a joke.

100,000 schools and 3.2 million teachers in the US.
Who pays for the guns, training, storage and insurance?

Also, most teachers would carry smaller pistols (lower weight, smaller size and low recoil). A cheap bullet proof vest can stop smaller pistol rounds cold.

So what is the point other than to distract from the problem and sell teachers useless guns?