If you are taking the class at a LQS, they probably expect you to buy at least some of the fabric from them as that gives them some compensation for offering the classes. I expect the instructor gets the bigger portion of the fee they charge for the class. The "one" class I took was like that. When they gave you the list of needed fabrics, they 'suggested' that you purchase from their stock. If you are taking a class somewhere else, buy whatever you like.