If the MacBook is less than a year old it is still covered by Apple's warranty. Contact Apple using expresslane.apple.com if you are in a country that supports it or call the appropriate phone number on this page. Alternatively carry the MacBook in to an Apple retail store or service provider.
It sounds, however, like it may have been refurbished by someone else, and thus not falling under Apple's warranty. Check with your school to see what the coverage is.
Best of luck.