There are others here that know more about it than me, but from what I understand you have two options:
1) Contact whoever holds the rights to the song and let them know you want to use it in a student production that you have no intent on making any money off of, and more often than not they'll give you permission to use it as long as you never make a dime off the film.
2) Use it without permission knowing that you will not be selling this piece. Just know that this could cause you major legal problems in years to come if for some reason you want to put it on a DVD.
Now, let all the people who know more than me about this subject come in here and tell you what a fool I am.
Poke