Sometimes the power will go to their heads and they're regard you only as 'the help.' They'll sometimes make you feel inferior and will undermine you in front of the students, just because they can. This doesn't go for every teacher, but you're bound to come across a few who don't do their research and when you're trying to discipline one of the students, they'll let them off. If you're a teaching assistant and you have any more problems to share, please write them in the thread below.