If a student registered for School A in the past but now attends School B, the student can log in to the student's account at TotalRegistration.net and click the Change Schools link in the Account Functions section to change the linked school.
NOTE: Changing the school linked to the student's account will not change the school exams are registered with. If the student needs to change their exam registration, the student needs to request exam cancelation at School A and then register at School B's registration site.