The watchdog charged with overseeing standards in many of England's top public schools has faced criticism for the way it has presented inspection findings.
Here is what you need to know:
What is the criticism all about?
Ofsted only inspects some independent schools. Others are inspected by bodies such as the Independent Schools Inspectorate (ISI) instead.
But, each year, Ofsted prepares a report for the education secretary about how some of these other inspectorates – including the ISI – have carried out their work.
For a report on the ISI, published last week, Ofsted looked at a sample of 11 inspection reports produced by the inspectorate in 2016-17.
It found that two of these reports gave schools a clean bill of health – despite finding leadership and management failings.
Because inspectors failed to reflect these failings in their overall judgements, the ISI flouted its own guidance, according to Ofsted.
Which schools are involved?
The ISI inspects nearly all of the schools that belong to the Independent Schools Council, which has more than 1,200 members, including many prestigious schools such as Eton, Harrow and Cheltenham Ladies' College.
However, Ofsted didn't name any of the 11 schools whose inspection reports it examined for last week's report.
How has the ISI responded?
The ISI has declined to comment on Ofsted's findings.
It's important to remember that problems were only found in two inspection reports; the ISI carried out 415 inspections in the year concerned.
But Ofsted was only able to get hold of 11 reports, and carrried out just two on-site visits of schools that had been inspected by the ISI.
Because of this, it "is not able to make any recommendation as to ISI’s suitability for continued approval as an independent inspectorate", it said. So the report in itself may not lead to any major changes to ISI's inspection regime.
Does Ofsted want to monitor more of the ISI's work?
Ofsted blamed its inability to reach any overall conclusions on the ISI's work on "the limited range of evidence from monitoring commissioned by the DfE".
A spokesperson for Ofsted told Tes that it "has not done routine on-site quality assurance monitoring of ISI since 2015-16", but did not expand on whether it would like this to change.
A move to scrutinise the inspectorate's work more closely may not be welcomed by the ISI or the schools it inspects, which value their independence.
A few years ago, independent school headteachers reacted strongly to rumours of a plan to impose an Ofsted-style system of inspections on them, which they worried would be more "cumbersome" and involve more "box-ticking".
Doesn't Ofsted already inspect some private schools?
Yes. It inspects 1,097 "non-association" independent schools that are not members of bodies such as the ISC.
Last month, Ofsted reported that the proportion of these "non-association"schools that it judged to be “inadequate” had risen to 15 per cent.
The watchdog is also concerned that some "insular" independent faith schools are failing to promote British values.