Abstract: A mounting base secured to the rear bumper of a school bus pivotally supports at least one step plate for movement between an operative horizontal position extended rearwardly of the bumper for use by children exiting the bus by way of the rear emergency door, and a retracted vertical position extended upwardly adjacent the rear end of the bus. A catch mounted on the emergency door of the bus is arranged to extend downward sufficiently to overlap the retracted step and secure it in retracted position when the emergency door is closed. When the door is opened, the catch is moved therewith away from the step, whereupon the latter swings downward to the operative horizontal position.