Financial problems and dwindling pupil numbers at top private schools could force at least a dozen independents out of the elite Headmasters' and Headmistresses' Conference (HMC), TES has learned.
An acrimonious debate is understood to be taking place at the heart of the HMC, which represents the likes of Eton College and Harrow, over whether to stand by schools that are struggling or cut them loose and focus instead on its larger institutions. A senior HMC source said that some people in the organisation also wanted to recruit high-performing girls' schools.
The HMC is concerned about at least 12 schools, the source said, where pupil numbers are in danger of falling below 325, the minimum required for membership. There are also concerns about the financial health of a number of schools that have been hit by the recession.
The issue came to light as Llandovery College - one of Wales's top independents - was told its HMC status was hanging in the balance because of low pupil numbers and revelations about pound;2 million worth of long- standing debts.
The poor state of its finances led to teachers receiving no pay for June, although a rescue package means all staff will be made redundant and immediately re-employed in time for September. The school hopes to have 320 pupils in the new term.
Headmaster Guy Ayling, who took up the post in April, told TES that he had written to the HMC, which represents 250 schools, in "support of the many schools that may be struggling in these difficult times".
"The HMC seems to be whittling away at the schools on the periphery and, from the reaction of members, this is not a popular policy," he said.
Independents in the North East, North West and South West have been particularly affected by the recession and a surplus of schools. The Independent Schools Council census showed that the overall number of private school pupils was up by 0.1 per cent in 2012 - the first increase since the credit crunch hit - but that was fuelled by the popularity of schools in London and the South East. In other regions, pupil numbers fell by 0.7 per cent.
The debate has been sparked by an internal review of membership rules carried out this year. Losing the HMC seal of approval would be a blow to schools that are already struggling, as it is seen as a mark of high quality among parents. Status is reviewed only when a school's leadership changes, as the membership is granted to the headteacher.
"There have been very acrimonious discussions, with one side saying we should actually raise the pupil number requirements and recruit strong girls' schools," a senior HMC source told TES. "The other side says that we should abandon size as a requirement, focus on quality and the strong should help the weak."
The HMC has only one all-girls member - Guildford High. Most high-ranking girls' schools belong to the Girls' Schools Association.
Lord Adonis, the former Labour schools minister who oversaw the transition of a number of independent schools to academy status, last month wrote that "the chill is serious" for many private schools and a number might not survive.
A handful of schools have already sought a way out through taking on academy or free school status - for example, Batley Grammar in Yorkshire and most recently Liverpool College. This has led to more soul-searching at the HMC over the new status of members who effectively become publicly funded competitors.
As well as the requirement to have at least 325 pupils in total, schools also need their sixth forms to be equivalent to at least 60 per cent of the number of pupils in Years 9, 10 and 11 to qualify for HMC membership.
HMC chairman Kenneth Durham, who is the headmaster of University College School in Hampstead, north London, denied that there was a rift in the organisation and said that debate over what should happen to schools was "extremely amicable". He also disputed that as many as 12 schools were in difficulties.
"We raised the size requirements in 2007 from 250 to 325 and any schools that didn't reach that threshold were allowed to stay in," he said. "I suspect that some of these schools may be finding it hard to reach that figure because it is not a good time to seek to expand your school."
General secretary William Richardson said no decision over possible rule changes had been reached. It was unlikely that an incoming head would be excluded from membership solely because the size of the school had shrunk, he said.
Ups and downs
0.1% - Increase in overall pupil numbers at independent schools.
1.2% - Increase in overall pupil numbers in London and the South East.
-1.8% - Drop in day pupil numbers in the North of England.
-1.3% - Drop in boarding numbers in the South West.
-3.1% - Drop in boarding numbers in East Anglia.
Photo: Llandovery College was told its HMC status was hanging in the balance.
Original headline: Elite private school group may force out `struggling' members