S.C. Code Ann. § 59-67-110: Front entrance-exit; emergency exit.

Every school bus shall be provided with a front entrance-exit on the right side of the vehicle and a rear emergency exit or door, conspicuously marked on the inside "emergency door" and equipped with a fastening device capable of being quickly released in emergency but entirely safe from accidental opening upon the application of any pressure from within the bus. Except in the event of an emergency, no person shall be allowed to enter or leave the bus by any other than the front entrance-exit.