More than 100 outstanding schools have been stripped of the top rating by Ofsted because their teaching was not of the highest standard, it has emerged.
As part of major changes to inspections, announced last year, schools were told that they were unlikely to be given the top ranking unless their teaching and learning was at this level.
New figures published by Ofsted show that since last September, when the changes came into force, 155 schools have been inspected that were rated as outstanding overall, but were less than outstanding for the quality of their teaching.
Of these, 91 have now had their overall ranking downgraded to good, 18 were found to "require improvement" and two were declared inadequate. Around 28% (44 schools) retained the outstanding rating.
Ofsted said that outstanding schools are not usually inspected unless a risk assessment triggers a visit, or there is significant change to the school.
A number of factors, including a drop in attainment, may contribute towards an inspection being triggered, the inspectorate said, adding that a decision to inspect may be due to a number of reasons, not necessarily linked to the quality of teaching.
An Ofsted spokeswoman said: "The inspection framework introduced from September 2012 raised expectations. Teaching is, of course, central to the life of every school. That is why there should be a close link between Ofsted's overall effectiveness judgement and the quality of teaching.
"It makes sense that outstanding schools should have outstanding teaching - parents expect that. This doesn't mean that every lesson needs to be outstanding but, over time, schools must show outstanding teaching is helping pupils make excellent progress."
Ofsted figures show that as of the end of August last year, a fifth of schools (21%) in England were judged to be outstanding overall - around 4,442 schools in total.
Of these three-quarters (76%) were rated outstanding for teaching, while the rest had teaching which was considered good.
Christine Blower, the general secretary of the National Union of Teachers (NUT), told BBC News online: "By constantly changing the goal posts of what constitutes a good or outstanding school it makes it very difficult for schools to reach the targets imposed by Ofsted and Government.
"This is especially the case for schools if they serve in challenging communities as less and less attention is given by Ofsted to the value schools add to their pupil achievements in relation to their low starting point."
An overhaul of inspections was announced by Ofsted chief inspector Sir Michael Wilshaw last year.
At the time, Sir Michael said there needed to be "clear and demanding criteria" for a school to be judged good or outstanding.
This means that outstanding schools should have outstanding teaching, he added.
Concerns had previously been raised that a number of schools have been judged as outstanding by inspectors, despite not receiving this rating for their teaching.
It was suggested that up to 1,000 outstanding schools could have their status reviewed. Ofsted insisted this would not mean a return to routine assessment, and that decisions on whether to review schools will be made based on risk assessments.
Other changes to inspections included scrapping the satisfactory rating and replacing it with "requires improvement".
Ofsted now inspects schools on four categories - achievement of pupils, quality of teaching, behaviour and safety of pupils, and leadership and management.
It was also revealed today that two more free schools have been rated as outstanding by Ofsted, while another has been ordered to improve.
The Priors School in Warwickshire was found to require improvement following a visit by inspectors last month.
A report on the school said that there was not enough good and outstanding teaching and that in some lessons pupils did not learn quickly enough because activities "do not always offer the right amount of challenge, particularly for more-able pupils". In these lessons, pupils often spent too much time listening to the teacher.
Ark Atwood Primary Academy in Westminster, London, and All Saints Junior School in Reading were awarded the top ranking following an inspection earlier this month.
Inspectors found that pupils at Ark Atwood Primary made excellent progress, that behaviour was excellent, that their "highly positive attitudes contribute strongly to their progress" and that teaching was "consistently good and often outstanding".
And the inspection report on All Saints Junior concluded that children made "excellent and rapid progress" from when they started at the school, and that youngsters showed "a substantial love of learning" and had very high expectations of themselves.
The schools were among the first of the Government's flagship free schools, opening in 2011.
In total, 22 of the first 24 free schools have now had Ofsted reports published. Four have been rated outstanding, 12 were found to be good, five were considered to require improvement and one was inadequate.
A Department for Education spokeswoman said they were pleased that nearly two-thirds of inspected free schools had been found to be good or outstanding.
"Where inspectors found a handful 'require improvement', we are confident they are taking the right steps to improve standards," she said.
"Schools rated 'inadequate' are eligible for intervention. They must take urgent action to improve and will face decisive action if they are unable to demonstrate good enough progress."