Abstract: There is provided a new and useful alarm system for use on a school bus having an ignition switch, a master switch, a rear door switch, the alarm system comprises a plurality of electromechanical circuits arranged so as to effect a resting state in which the system is inoperable, a stand-by state activated by actuating the ignition switch, a latching state from which the system may be armed, an armed state in which the system is operable, alarm means to indicate an alarm state, and a disarmed state in which the system is deactivated. There is also provided deactivation means positioned at a rear of the bus to deactivate the alarm system while in the armed state or the alarm state, wherein the alarm system is integral with the ignition switch, the master switch and the door switch of the bus.