Most likely this wont be an option in an actual art class.
We had a model that knew someone in the class this semester it took an hour and a half to covince her to model and she ended up being wrapped in a sheet. Kind of defeats the purpose, in a figure drawing class when half the figure is covered.
I say just act like you've done it before, and ask the teacher to tell you the exact poses or types of poses she/he wants, that'll take a lot of the guessing out of what you have to do.