I think Master Wang-Ka’s letter is awesome and wholly appropriate. Use it!
I had a similar situation at my most recent job—they had morning classes that were mandatory, and they’d expect the evening and night people to work 16 hours a day (8 hours work, 8 hours class). God forbid they allow us any sleep, or anything. And our job duties involved direct care of patients: giving meds, baths, etc. Not something you really want to do when you haven’t had any damned sleep.
Fortunately, I knew that the powers that be could not force us to work any overtime. So when I saw on the schedule that they’d had me down for 16 hours, I would call up the supervisor and tell her to pick one shift, 'cause I wasn’t doing both. (And then they’d change the schedule for me.)
It was amazing, however, how many employees thought that since it was written on the schedule, they had to do it. I think the bosses exploited this: the figured, they’d put any absurd, beyond-unreasonable thing on the schedule, just to see if it’d stick. With most employees, apparently, it would.
I did hate, however, having to work an evening shift (getting off at 11 pm) and then having to get up at about 6 am, in order to leave at 7 am to drive an hour down to where the classes were being held. (Yes, we had to drive an hour.) I would be so tired I was barely able to function, but hey! I was there.
One time I was driving down there, running a little late (with almost zero sleep because I couldn’t get to sleep the night before) and I got pulled over for speeding. Yes, I was speeding. I was also incoherent with exhaustion. I was very contrite to the cop and explained why I was so tired and what my employers expected of me (my employers were big in that town and everyone knew of them) and he was sympathetic. Enough so that he let me off with a warning. (The first he’d given that day, he said.) There’s something to be said for being pathetic, I guess.
Another thing that irritated me was when I’d drag myself down to the class (hour drive, remember) only to find out that they’d cancelled it and never told me. They did this several times. Typical inteptitude.
Also, I knew that they had classes in the evening (during my normal shift) but was I ever allwed to attend those classes? Oh, hell no. Because that would interfere with my 8 hour shift and we couldn’t have that. They didn’t want to find anyone to cover me, so much better to drag me down to the class with no sleep than to allow me to just go to the class during my regular working hours.