Yes, they can do this, unless:1) There was some written agreement specifying what classes you'd have to take--if there was, then they could not violate its terms (unless the agreement also stated by its terms that it could be altered by the college); or2) You feel you can show that they deliberately lied to you to get you to sign up--basically, that they knowingly did a "bait and switch" to you, which may be fraud.