The bus company’s X15 service recently failed to arrive to take pupils back to Belford after they had finished for the day at Duchess’s Community High School in Alnwick.
The latest incident took place on December 14 but there have been three other occasions in the past month.
An Arriva spokesperson, speaking after the latest incident, said: “There have unfortunately been a number of impacted services across this network – linked mainly to congestion along key parts of our routes.
"As well as this, we experienced a vehicle breakdown which was dealt with as quickly as possible and a new bus was allocated to the route to ensure minimal impact to ongoing customer journeys.
"We constantly review our service delivery and fleet allocation, taking into consideration as much as possible external factors such as congestion.
“We apologise for the inconvenience caused, to any of our customers, as a result of the numerous issues on our services.”
Belford councillor Guy Renner-Thompson said: “I have been inundated with messages from parents who have had to make the journey into Alnwick from Belford after the Arriva X15 failed to bring their children home.
"This is simply unacceptable. With cancellations and delays, kids aged as young as 11 are routinely doing longer days than many adult workers.
"The council have raised this with Arriva and if satisfactory answers can’t be given, the council will look at alternative options.
“It’s my preference for a local company to take back control of the school bus service. We never had these problems when Belford company ‘Travelsure’ ran the service.”