I did CNA work at a hospital while in nursing school and it was the best thing I did. It certainly isn't going backwards as if you get in with the right nurse they will teach you things and let you do things to "help" them while learning at the same time. If the hours aren't good, then you need to just say something once you're in the door. Besides, if it's in a hospital, it may also give you a foot in once you graduate.