You have gone off the deep end.
Consider how the situation would be if the families were allowed to sue the schools for the loss of their children? How much would the school spend to avoid this? Then suppose that the school could avoid these lawsuits if and only if they show that a certain percentage of adults on campus were carrying concealed firearms and taking regular firearm training. Finally, you would exempt these armed adults by what one sheriff is doing, Making them official deputies while they are acting against an active shooter incident on the school grounds. They would in turn be responsible for any accidental discharge of the firearm., An official signal would be needed to release this awesome team activity and that would be the signal that immunity from prosecution was in force. BTW, this certainly beats urging your class to get down on the floor and blocking the shooter’s path with your unarmed body.
I have seen other things proposed but all are costly and also turn the school into an airport. Can you imagine how long a fire alarm would take if your entire student body had to leave the building and then enter via one or two checkpoints? How many guards would be necessary to wand every student who failed the metal detector or backpack?
The sheriff who offered training for faculty (looking for a class of 50) ended up with 250 applicants. I agree with Trump that you must have an offensive capability to act while waiting for the actual police to arrive. The idea he came up with was to pay these teachers a bonus (and while you would admit you had armed faculty, the actual carrying faculty members would not be disclosed.
No faculty member would be prohibited from joining this tactical group unless they failed the physical and training requirements. However no faculty would be required to do this as a condition of employment.
It seems to me that this would be similar to when I was teaching and coaching the JV Soccer team. It was not required but while I was trying to get tenure, it looked good for me to have the additional responsibility.
If you don't include the requirement to be armed as a part of the job description, and without making it an option, the concept is simply not realistic. Otherwise, it is rather snow-flakey in its utopian assumptions.