BULL LARKEY! That means ...well you know!
If the n-g tube comes out and he's hooked up to the pump, then turn the pump off and call mom. No big deal.
If he's not hooked up to the pump and it comes out.....put it back in later.
The nurse (we have real certified nurses here) HAVE to accommodate your child. If they won't they have to send to tutor to your home and most school district won't want to pay for that.
Find out your rights in the school and talk to the principle, nurse and teacher.