Girls' schools such as Roedean, Cheltenham Ladies' College and Malvern Girls' College are charging record-breaking maximum fees for some pupils in the sixth form.
It is the first time that mainstream schools have broken this psychological barrier, putting them in the same bracket as super-luxurious international and finishing schools.
Top fees at the girls' schools are now up to pound;600 a term more than those at Eton, although in some cases Eton's basic fee is higher. But the schools insist they promise value for money. A Roedean spokeswoman said the top fees were only payable by those joining in the sixth form and added that it only topped the table because, unlike other schools, equipment and activities are included in the fees.
Sam Hesketh, bursar of Malvern Girls' College, also said the top fee is only charged to girls who join in the sixth form. "It is not the common fee for every girl in the school," he said. The standard fee is pound;6,127 a term.
This academic year also sees a surge in the number of schools charging more than pound;6,000 a term, from six to at least 45. Almost all of England's famous schools, including Eton, Harrow and Rugby, now charge more than pound;18,000 a year, as does Tony Blair's alma mater, Fettes, whose maximum fees stand at pound;6,022 a term. Fees at top schools are up 7 per cent on last year, well above the rate of inflation.
Schools said the increases had not put parents off. The Independent Schools Council's Dick Davison said: "We were asked a similar question a few years ago when fees rose above pound;5,000 a term, but there was no obvious effect then." Sheila Cooper of the Girls' Schools Association said that girls' schools still tended to charge less than boys'.
Meanwhile, day fees are creeping up, with 22 schools in London and the South charging more than pound;3,000 a term compared with five last year. King's College School, Wimbledon, is the most expensive day school, charging pound;3,560 a term.
Maximum termly fee for a boarder, often only paid by sixth-form entrants:
Roedean, Brighton: pound;6,990
Cheltenham Ladies' College: pound;6,889
Malvern Girls' College: pound;6,750
Gordonstoun, Moray: pound;6,625
Winchester College: pound;6,548
Wycliffe College, Gloucestershire; pound;6,505
Benenden, Kent: pound;6,500
King's School, Canterbury: pound;6,445
Bryanston, Dorset: pound;6,409
Wellington College,Berkshire: pound;6,385
Tonbridge, Kent: pound;6,381
Harrow, Middlesex: pound;6,375
Millfield, Somerset: pound;6,375
Bedales, Hampshire: pound;6,369
Eton College, Berkshire: pound;6,366