I've had coworkers in the past have issues with a night class once a week and some were able to take that one day off a week for the semester, others were told to transfer to midnight. I guess it all depends who your boss is, if they like you, etc. I was never too worried about those people. School is important and sometimes colleges have classes in some wacky inconvenient time slots that conflict with UPS.
I see that many people have different views on this issue. I wonder as to why there is nothing in the contract to mediate these types of things. I guess it just depends. :/