What must a school bus driver do before leaving the driver's compartment when a pupil is aboard?

A school bus driver must stop the engine and remove the key before leaving the driver's compartment when a pupil is aboard to ensure the safety and security of the students. This procedure is critical because it prevents any unauthorized use of the bus and minimizes the risk of accidents, such as the bus inadvertently moving while a child is present.

Stopping the engine is important for safety reasons; it reduces the risk of accidental operation of the vehicle while the driver is away from the compartment. By removing the key, the driver ensures that no one can start the bus while pupils are still on board, effectively safeguarding the children from potential misadventures or injuries.

While setting the parking brake is also a critical safety step, it alone does not provide the same level of security as removing the key does. Calling for assistance is not a requirement or a standard procedure in this context; the priority is to secure the bus and its passengers. Thus, stopping the engine and removing the key is the most comprehensive and protective action a driver can take.