That's pretty good for a school poster. The wally is pretty awesome and I agree with MD's comments although I have to add 2 more things.
Uno-) The text needs a little bit work, not only the A LYKEIOU one.
Dos-) It lacks a focal point. I mean I don't know where to look, her boobs, her face, what? It's a little messy this way.
And from my personal experience I know your classmates will love it cause I guess they know shit about photoshop. Personally everything I made for those partys they were like "OMG wtf" although it pretty sucked :P. Good Job