He also warned that private schools risk being distracted from teaching by focusing on building new facilities, which also leads to fees rising.
“In previous generations we would have put up with Portakabins, but you can’t do that when you are catering for people with super-yachts,” he said.
“Schools used to show off their swimming pool, now they show off their theatres, fitness studios and recording suites.”
The figures come as St Paul’s School in Hammersmith announced plans to give bursaries to boys whose families earn up to £120,000 a year. Previously the figure was £60,000. Boys will also have to meet the school’s academic criteria. Fee sat St Paul’s are about £23,000 a year. A £77 million rebuild at the school will include a new drama centre and theatre.