When you graduate, you should contact the credit card issuer. You may be able to keep the student credit card or upgrade the card to a regular version of the same card or a better card.
You might also qualify for a higher credit limit.
If you do end up keeping the student credit card, use it occasionally to keep it active. One factor that contributes to your credit score is the length of your credit history and having a card open for a long period of time can impact your score positively.
For this reason, it is good to keep your oldest cards open, unless, of course, the cards charge an annual fee and you do not receive value that exceeds that annual fee.