That's a plausible scenario, but even in that scenario, I'm not sure how being able to run an 8 minute mile, do a bunch of sit ups or jump 14" in the air will make much of a difference. If that scenario is your concern, why not at a requirement that all armed teachers must all be black belts in martial arts?
Besides. Having one's EDC sidearm taken from them is a risk every armed citizen runs, yet we don't deny the 2nd amendment to citizens based on that. All I'm asking is why teachers, in this bill at least, are being required to meet standards that other citizens are not required to meet.