From Snopes...
http://www.snopes.com/disney/films/sots.asp
Basically although the NAACP expressed concern over the film at the time, the NAACP doesn't really have a position on it now.
Honestly, given the class that these students were in, the Professor could probably have showed it in class without anyone batting an eyelash.
However that invite from the Student, definitely out of bounds...
The other movie that has run into Racist concerns is Fantasia, but that was handled with relatively small cuts.