A family in the eastern Ontario community of Kemptville wants to know how their five-year-old son ended up trapped in a locked school bus for more than three hours without anyone noticing.

John and Jen Mayor say they want to know why so many guidelines were not followed resulting in thier son being locked inside a school bus. (CBC)

John and Jen Mayor said their son, Kaiden, boarded his school bus at 8:45 a.m. on Thursday. He fell asleep on the bus, and after other students were let off at Kemptville Public School, the bus driver parked the bus near his home.

The driver then locked the bus and went inside his home, not realizing the child was still on the bus.

Drivers are required to visually check all the seats on the bus after the children have left.

The school should also have called the parents when the child failed to show up for class, said Greg Pieterson, chair of the Upper Canada District School Board.

That didn't happen. Instead, Jen Mayor was at home at about 1 p.m. when the bus driver dropped her son off and offered a tear-filled explanation of what had happened, saying he had discovered the child when he returned to the bus to do an afternoon run.

'How many levels had to fail?'

John Mayor said too many things went wrong.

"We put our children on the bus every morning, they are our treasures … so we're expecting them to come back," said Mayor. "Accidents do happen, we understand that. But an accident like this, how many levels had to fail before my wife gets a phone call ... which she never received," said Mayor.

The bus driver dropped off students at Kemptville Public School, but didn't notice that one child had fallen asleep. (CBC)

Pieterson called the incident "a nightmare scenario."

"It's not good enough to even miss once, so we will ensure we put in additional procedures to make sure this doesn't happen again," he said.

The school board will investigate why procedures at the school were not followed, he said, while the regional bus authority, Student Transportation of Eastern Ontario, will investigate the bus driver's actions.

On Friday, the Mayors kept their son home from school, and the driver was not driving the route.