Students need an Apple id to purchase apps for their iPad. You even need one to purchase free apps. While everyone knows that but what you may not know is that you don’t have to attach a credit card to your account. To create an iTunes Store Account without using a credit card, following the instructions provided here: Create an iTunes Store Account without a credit card.
NOTE: You can always purchase an iTunes Gift Card to buy apps and music so there’s no real good reason to give them your credit card information.