Serious studies have shown that the only single measure that stops mass killings is concealed carry. Some flawed studies only included cases where more than 4 people were killed. That rules out all the examples of cases where the shooter was stopped.
All other methods: waiting periods, background checks, death penalty, increased penalties for committing a crime with a gun have had no effect at all on mass shootings.
Ironically, the places where most mass shootings occur are the supposed “gun-free zones”. Makes sense, because the shooter wants a defenseless crowd.
If we really care about saving lives of innocent people, we should look at the only policy that has ever been shown to work: concealed carry.
And if it is the teachers who are carrying, so be it.
For more detail on this argument, please see Ann Coulter’s We know how to stop school shootings