Mr H
Banana'd
Think it's more a concern of teachers not being trained in weapon retention. Also a matter of size. I don't worry about someone like Norton retaining a weapon. I do have concerns about someone like my daughter's teacher who is all of 5'3" and maybe 110 lbs.
This is the piece I think many people miss.
ANY carry should come with some level of assessment and training/practice.
We choose which firearm is suitable for us, personally. Likewise (in this example), teachers should be screened and trained to be effective and safe defenders.
After Sandy Hook, my wife was asked if she would carry. She responded that (paraphrasing), whether she did or not, it would be after serious training and assessment.