I also don’t think the majority of teachers need to be armed in school… It’s OK if it is a majority, but if you have 10% or a critical mass of 5-6 armed teachers and staff, that should generally do. Just as long as it’s not just one or two.
It would depend on the size of the school, as in number of teachers and actual physical area, in my opinion. Also, cooperation and communication with law enforcement who would be clearing the building would be a necessity- the potential for friendly fire incidents is enormous. Some procedures about firearms use would be critical to avoidance of those. Also, there would have to be a great deal of discussion about which arms to use- FMJ rifle rounds would be a poor choice as most schools are built of concrete blocks and the range in most cases relatively short. Simply saying “Arm the teachers” is one thing, and doing it is a bit more involved. It is still the most logical and fiscally responsible step, though.