The cost of private education for boarders has soared by 86% in the past decade with average boarding school fees now equal to 73% of the average annual income.
Research from Halifax reveals average boarding school fees were £20,970 in 2007, with the highest fees in London at £23,250 and the lowest in Wales at £18,540.
The increase in the cost of boarding school fees is nearly three times the rate of retail price inflation during the past 10 years. In 2007 alone, fees increased by 5%.
Halifax says boarder fees are more than double those for day pupils.
Official figures show the number of private school pupils (day and boarders) has increased by 7% to 669,300 since 1997. However, the number of boarding school pupils has declined by 14% from 77,876 to 67,335. This was offset by a 12% increase in day pupils.
Martin Ellis, economist at Halifax, said: "Boarding school fees have risen by significantly more than average earnings over the past five years.
“Parents need to plan their finances as early as possible if they want to send their children to boarding school."
Hilary Moriarty, national director of the Boarding Schools’ Association, says the increase in fees represents a rise in teacher salaries and pension costs.
She said: “Boarding school education still represents good value for money. Fee increases have helped bring boarding schools up to 21st century standards with more staff and better accommodation.”