Bullying and other misbehaviour on school buses is on the increase, a council report has said.
Problems were said to be worse on double-deckers, with coaches best
Bus companies were more reluctant to take on contracts and were putting up their charges, said a report by Buckinghamshire County Council.
It said some drivers' lack of fluency in English made it difficult for them to control children.
Sixty pupils were barred from school buses last term. But getting parents to accept responsibility was difficult.
A review by the council's Children's Services committee on preventing bullying said that during its review it had heard of an increase in recorded incidents of poor behaviour and bullying on some home to school bus routes.
"The rise in recorded incidents has been most pronounced in year groups 7 - 9, which the committee was informed is a national problem and links with increased poor behaviour of this age group within the schools.
"The result is that bus companies are reluctant to take on the school transport contracts and, where they do, they are increasing their cost estimates," it said.
"Some drivers do not have English as a first language, which may lead to difficulties when communicating with children and controlling behaviour."
The most severe potential sanction was a permanent ban from school transport.
This was rarely used, but fixed term bans had increased last year.
The committee felt parental involvement and support was crucial to managing the behavioural issues. A code of conduct is signed by parents and students.
"However, where incidents have taken place and students identified, it has been difficult on occasions to enforce the code of conduct which requires parents to accept full responsibility and pay any costs for damages," the report said.
One thing it suggested the county might consider is a "peer bus monitor" scheme used successfully in some other areas.
Sixth formers are recruited as bus monitors to support drivers, in return for free travel.