A Perth boy who was accessing educational support at a suburban high school was left unattended on a bus at the depot for close to five hours on Wednesday.
The Horizons West school bus returned to its depot at 9am, where the Year 7 student was left, alone, on board the bus until 1.40pm.
Perth's Public Transport Authority (PTA) said the boy, who attends Leeming SHS Education Support Centre, had food and water while in the parked vehicle.
He was allegedly found when the bus driver returned to the vehicle to begin his afternoon pick-up route.
In a statement, the PTA said it had strict rules regarding the operation of its school bus service, which requires the driver to search the bus at the end of each trip.
The PTA is investigating the incident but said it was clear the requirements were not met.
A bus driver and bus aide have been stood down until further notice.