I worked at a place like that before. New people and students were asked first because they usually had less scheduled hours so it was easiest to get them to say yes or avoid conflicts in the schedule. That's all it ever was and most of the time, unless a trade or shift give away was happening the manager never even knew.

But really, you're working at some job while going to school. Why do you care if your boss likes you or if you're doing a good job? It isn't career related is it? Just show up. Do the minimum and you will get glowing reviews and references because even the lifers don't do that much. And the student thing, there's hope for you so your manager won't screw you over when you ask for a reference when you get a better offer.