Nine vehicles in total were taken off the road in the city following a day of checks by the North’s Driver & Vehicle Licensing Agency.
They say faults found during the inspection of 24 buses ranged from defective seat belts to problems with emergency exits.
Stephen Spratt, chief enforcement officer from the Driver Vehicle Agency said the buses had to be taken off the road.
“There were six vehicles that were checked at the school. Four of these buses were found to be unfit for service.
“Of those four buses, three were operated by companies based in the Republic of Ireland and one was based in Northern Ireland,” he said.
“There were issues with seatbelts and emergency exits.
“We pay attention to everything from steering, brakes, tyres and the fixtures and fittings in the vehicle.
“We will be taking follow up action and we will be visiting the operators,” he said.