Inquiry into Dorset school bus problems
Dorset County Council is to launch an internal investigation after "teething problems" with its school bus services left some children stranded.
The authority, which changed the bus operator it uses for school services, said the situation was "unacceptable".
A spokesman said there had been a number of instances where children were not collected and journeys by operator Damory ran late or not at all.
Damory said it was working with the council to rectify the problems.
Dorset County Council said it used its own fleet and other contractors to cover five journeys in the past week.
Children's services councillor Toni Coombs said: "This is a new contract and we would always expect some teething problems as it beds in.
"However, the scale of these problems is unprecedented, and we appreciate that the effect is significant and a major concern to parents.
"Damory has been open in explaining the issues facing them in the implementation of this substantial new contract, and the number of the problems that have occurred.
"Following detailed discussions, our managers have been assured by Damory that it has suitable plans in place to correct the problems and improve performance.
"We are also launching an internal investigation to probe into the issues we've had with the transition into this new contract."
A spokesman said Damory was sorry for the problems "on a few of school services" it had taken over and said it was working to solve the "small number of problems that may remain" on the contracted services.
Since the introduction of the new service, ticket prices have risen from £250 to £400 and the number of spaces has been cut from 2,000 to 1,000.