Free schools will not be inspected by Ofsted to check their standards for up to two years after they open.
The inspection body said the schools will only be visited earlier if concerns are raised about their performance. The decision was revealed on Friday by Ofsted chief inspector Sir Michael Wilshaw who also said inspections for newly opened academies may also be scrapped.
One teachers' union said the move was "odd" and said it would make sense for Ofsted to check newly established schools.
Under the current system, schools - usually those rated outstanding or good - which "convert" to become academies, or academies that take over failing schools, receive a "section 8 visit" a few months after opening to check on their progress.
Sir Michael told the Independent Academies Association these will be stopped. Instead, the academies will receive a usual full inspection when it is due, based on the performance of their predecessor school.
He told delegates: "Academies are becoming a larger and larger part of the school system, and it's important we have a consistent approach to inspection for all schools.
"So from September, my intention is that newly opened and converting academies will not have section 8 monitoring visits, unless of course the previous school was in special measures.
"Although converting academies are new schools, it's right to take into account the history of the predecessor school when we are deciding when to inspect next."
It later emerged that this change will also apply to free schools, which are entirely new semi-independent state schools, without a history.
An Ofsted spokesman confirmed that from September: "There will be no monitoring visits to free schools unless HMCI has specific concerns. They will receive a full section five inspection around two years after opening."
It means that a pupil could spend two years being taught in a new free school before it is inspected.
Christine Blower, general secretary of the National Union of Teachers (NUT), said: "It is odd that Ofsted would wish to step up inspections to schools judged as outstanding but are quite happy for a new free school to operate with no inspection at all for at least two years.
"It would surely make more sense for Ofsted to use what resources they have to check on newly established schools with no previous track record and no support or help from the local authority.
"Yet again Ofsted appears to be reinforcing the political agenda of the present government rather than maintaining an independent and balanced view of their role."
Free schools are a flagship measure of the ogvernment's education policy. They are set up by groups including parents, teachers, charities and other organisations, and receive their funding directly. They also have more freedom than local authority schools on areas such as the curriculum and staff pay and conditions.
The first 24 free schools opened last autumn, and a further 79 have been approved for opening from this year onwards.Suggest a correction