Hutchesons' Grammar is one of the schools whose status is at risk
Four of Scotland's leading private schools have been told they must implement changes in order to keep their charitable status.
The affected schools are Hutchesons' Grammar in Glasgow, Lomond school in Helensburgh, St Leonards in St Andrews and Merchiston Castle in Edinburgh.
The Office of the Scottish Charity Regulator (OSCR) said that on balance "they do not provide public benefit".
It added it expected to see changes within "a reasonable time period".
OSCR's chief executive Jane Ryder said that after looking at the four institutions it was concluded that they did not meet the public benefit test.
She added that the failure was mainly due to significant fees and the fact there was not sufficient help in place for those who could not pay those fees.
ADVICE TO SCHOOLS
Produce within 12 months a plan to meet the public benefit test
To implement that plan within three years
OSCR must be notified within three months whether school intends to comply
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Ms Ryder said: "We are not dictating a particular business model to the charities and there are different ways in which they can address our concerns.
"But we are looking for an early acknowledgement of the intention to introduce changes and for implementation within a reasonable time period."
The head teacher at St Leonards School, Dr Michael Carslaw, said he was "greatly disappointed" by the OSCR decision.
He said: "St Leonards is established as a charity for 'the advancement of education for the public benefit' and it is my intention that this remains the school's objective.
"It is disappointing that providing a high quality of education is, in itself, not judged to have sufficient public benefit."
However, Dr Carslaw added that the benefits of being a charity were "limited to partial relief on rates and relief on corporation tax".
Under new rules private schools must be able to demonstrate they have a charitable aim and serve a cross-section of the public by offering places to children from disadvantaged families, or making their facilities available to the local community.
A total of 11 private schools across Scotland have been inspected by the Office of the Scottish Charity Regulator (OSCR) to see whether they qualify as charities.
Nationalist MSP Christine Grahame told BBC Radio's Good Morning Scotland programme that some "elitist" private schools did not deserve to receive charitable tax breaks.
She added: "A charity must have a wider public benefit, and if the fees are restrictive such as, for instance, they are at Gordonstoun - where I understand it is about £18,000 a year - then they must have more bursaries and be more open to the public.
"Apparently the schools that have been listed this morning have failed some or all of those tests.
"Certain private schools are so elitist that I can't see how they can maintain charitable status. The huge tax breaks they get are public money that is subsidising really quite well-off people."
But Frank Gerstenberg, former principal at George Watson's College in Edinburgh, said private schools actually benefit the taxpayer.
He added: "These are among the best schools in Scotland, produce the best exam results and relieve the taxpayer of a huge amount of money because parents are already paying for their children to be educated in the state system but choose not to."