It's the smart thing to do?
Is it?
We should know by now that the more hoops you make people jump through to do something, the fewer people there are who will do it. We see it with carry licenses, make it take more time, more effort, more expensive, and fewer do it.
The more training you require of anybody to arm themselves, in this case teachers, the fewer there are who will do it...which lessens the chance of there being one in the right place and time to make a difference in the future.
And there is of course the co$t.
Millions of people are licensed to carry, or legal to carry in Constitutional carry states, without any training requirements or mandates, and they are doing just fine. I don't see why teachers that are allowed to carry would need to have this huge level of training