One of England's greatest independent schools, Winchester, has admitted that the way schools exchanged information about fees might have broken the law.
Winchester is being investigated by the Office of Fair Trading
Winchester's headmaster, Tommy Cookson, told parents the exchange "appears to have been standard practice throughout the independent sector for many years".
"There has been no profiteering."
Winchester and an unnamed number of other schools are being investigated by the Office of Fair Trading (OFT) for possible breaches of competition law.
Computer systems breached
In a letter to parents, Mr Cookson also said "privileged information" about the affair had been obtained by some newspapers from the school's confidential computer systems - possibly with the involvement of "one or more boys in the school".
The Times newspaper has said that documents it has seen revealed that bursars at dozens of schools had exchanged e-mails containing details of proposed fees and costs as they prepared recommendations to their governing bodies for this year's record 9.5% average increase.
Mr Cookson said in his letter that the school was co-operating fully with the OFT enquiry and until it was complete there was little the school could add.
But he said it was now clear that the sort of exchange of information schools had engaged in "could be an infringement of the Competition Act 1998 which came into force in March 2000".
"To my knowledge, schools have made no attempt at any stage to conceal what they have been doing."
As an educational charity it had no incentive to charge parents more that it needed to cover its costs and make a small surplus which was reinvested in the school.
The big increase was due principally to three external factors "imposed on us by government policy" - the rise in national insurance contributions and pension costs, and higher teachers' salaries in state schools.
Winchester, founded 600 years ago, this year retained its position at the top of the private schools' A-level league table.
Its warden (the head of the governing body) is Sir Andrew Large, a deputy governor of the Bank of England.