Caveat: this program may not have existed when you served,
@DocIllinois, so you may not have known about it. Having said that, the Troops To Teachers program is a successful program.
This link shows their FY2016 numbers.
Reading many of your responses in this thread, my perception of your view of teachers is that they would be reticent to even accidentally gaze upon a firearm, much less operate one inside or outside a training environment. And most of them are, yes. However, this program demonstrates that there already are teachers with at least a minimum of military training out there in the schools. Given, I haven’t had the time to suss out the breakdown of participants by MOS, but it’s fair to say that the combat arms MOSs are not excluded from this program.
Adjusting for the existence of those participants who would never touch a gun again if their lives depended on it, and the disproportionate representation of the southern states in the military coupled with the likelihood of their returning to where they came from after retirement/ETS, it was more likely that the Florida shooter would run into a veteran/teacher than the Sandy Hook shooter.
As teachers, these veterans would already understand the concept that their job would not be to close with, engage, and destroy the enemy. Rather, the expectation would be to mount an armed defense of their students in whatever area they were forced to take cover. Or, should they be caught in the open by the antagonist, to engage as such to enable their charges to escape and take cover.
Given that the shooter would most likely believe that 100% of his adult targets are unarmed, the presence of just one adult firing a bare minimum of suppressive fire (if brandishing alone didn’t do it) would upend his apocalyptic delusion of grandeur and likely end with a fatal, self-inflicted wound to the antagonist. Remember, these school and church shooters aren’t battle tested CQB masters re-enacting the storming of Beslan, they’re unstable menaces that —had the laws already in place been followed — shouldn’t have been able to legally procure weapons to start with, and are following a “tactical plan” that was probably written by the underpants gnomes.
For the majority of teachers that aren’t prior service, let the decision to carry be 100% voluntary. Teach them how to hit what they aim at, and that they are there to defend whatever classroom or closet they are barricaded inside of, not to get their SWAT on. Let the counteroffensive be the bailiwick of armed security or law enforcement (assuming that they aren’t made of the same stuff as Broward’s Cowards).