Parents Sarah Ballard, Tania Baird and Penny Bingham with children dependent on the bus Parents have hit out at rocketing school bus fares, warning the rises will increase road congestion and discourage students from staying on at sixth-form.

Some families say they had no advance warning that Oxfordshire County Council was almost doubling concessionary charges in a bid to recoup a £564,000 budget overspend.

Fares have gone up from £120 to £221 a year for pupils living less than three miles from their school, and from £201 to £305 for those living more than three miles away.

Mother-of-two Sarah Ballard, 40, of Leys Road, Cumnor, whose 12-year-old daughter Jessica takes a two-mile school bus journey to Matthew Arnold School, said: "I was absolutely gobsmacked to discover at the start of term that the fares had almost doubled from £40 to more than £70.

"It's chaos with the number of cars outside the school in the mornings and this is going to encourage even more parents to drive their children to school."

Neil Darlington, the council's education officer for transport and admissions, said information about the price increases was available to anyone from March, but was not sent out directly to all parents.

He said: "The charges have gone up a lot but it is becoming more and more expensive to provide the same transport for these thousands of children."

Oxfordshire has 86,000 pupils. Free transport is given to children aged eight and over who live more than three miles from their school, and to pupils less than eight who live more than two miles away. All sixth-formers have to pay for transport.

Kate Moore, spokesman for the education authority, said: "We provide free travel for more than 12,000 mainstream pupils and 2,000 children with special educational needs. The concessionary places for which we have to charge represent 2,300 pupils."

There was consternation for families in Long Hanborough when Bartholomew School, Eynsham, failed to inform them that free travel was not available to sixth-formers and they would have to apply for a bus pass. As a result, there were not enough travel places available at the start of term.

Linda Munro, of Long Hanborough, said her 16-year-old son Alex had not been allowed on the bus to Bartholomew School several times since the start of term.

She said: "I didn't know I had to apply for the pass, it's always been sent automatically before. I'm not against charging 16-year-olds because they don't have to go to school, but £75 a term seems excessive."

Alison Gosling, 47, whose 16-year-old daughter uses the same service, said: "Charging this amount for 16-year-olds to go to school is not much of an incentive for them to continue their education."

Bartholomew head Andrew Hamilton said: "A letter normally goes out to prospective Year 12 parents at the end of the summer term. With major changes in the staff room, that didn't happen. A note is going in the sixth form prospectus to make sure parents are aware of this in future."