Are you sure its Hep B (and not C)? Hep B tends to be an acute infection, and is only rarely a chronic process (unsure what you mean by carrier). Either way they can test your blood for the virus itself and for antibodies against the virus (which confer immunity). Check with your school and find out if proof of immunity is enough. And if you have a chronic infection, plz see a doctor and get treatment.
Either way, ask your school.