And people wonder why I hate unions? It shouldn't be against the law to go the extra mile for your students if you're willing to do so. The union should be there to protect you from being required to work unpaid hours, but if you're willing to do it out of your own concern for the students, the union should be told to shove off.
Where were you a TA that other TAs would report stuff like that to the union? When I was a TA, we all scoffed at the union and were pissed that they deducted money from our paychecks whether we wanted to be a part of it or not. There was some minimum amount they deducted no matter what, and if you officially "joined" then they deducted more...we didn't really think that was helping us much. The only people who were actually "into" the whole union thing were the technicians, because they wanted to be sure they could just drop everything and walk out the door at 4 pm when their work day ended.