Schools in England will face no-notice inspections
All schools in England will face no-notice inspections from the autumn, the new head of Ofsted has announced.
Sir Michael Wilshaw said the move was a "logical" progression, adding that it was vital that the public had confidence in inspections.
But school leaders said they had "real doubts" that the plans would improve the inspection process.
They also raised concern that the change had been announced without consulting head teachers.
But Sir Michael, who took up his chief inspector post last week, said inspections taking place without notice provided an opportunity for inspectors "to do what's really important - going in and inspecting quality, particularly teaching".
He added: "Ofsted has been moving towards a position of unannounced school inspection over a period of years.
"I believe the time is now right for us to take that final step and make sure that for every school we visit inspectors are seeing schools as they really are in the corridors, classrooms and staff room."
Currently schools receive two days' notice.
Over the past 18 months, Ofsted carried out 1,500 no-notice inspections of schools causing concern. This included a pilot of unannounced visits to schools where there were issues concerning behaviour.
Sir Michael admitted that some schools may be wary of the change.
"In my experience, anything that's new is going to be treated with some nervousness by schools."
Sir Michael said he wanted inspectors to spend "as much time as possible in the classroom".
"I don't want them to spend a huge amount of time looking at documentation, there's too much of that. I want them to go in and observe lessons."
Education Secretary Michael Gove said he warmly welcomed the moved: "No-notice inspections, especially where behaviour and teaching standards are of concern, will provide parents and others a true picture of schools' performance.
"I look forward to receiving the full proposals in the coming weeks."
But the Association of School and College Leaders said no-notice inspections would not improve the effectiveness of inspections.
General secretary Brian Lightman said: "We welcome moves to improve the effectiveness of inspection, but I have real doubts that no-notice inspection will accomplish this.
"An effective inspection system is based on mutual trust and respect, not the premise that schools are trying to 'cheat' and need to be caught out.
"If inspection is going to lead to improvement, it needs to be done with schools rather than used as a beating stick.
"We have already voiced serious concerns that the Parent View website provides no way of ensuring that the views expressed are accurate or representative."
The National Association of Head Teachers said the move to no-notice school inspections was an empty gesture which would "alienate schools while doing nothing to support rising standards".
General secretary Russell Hobby said: "If a school could conceal evidence of widespread failure in just two days then the whole concept of inspection is flawed and Ofsted's protestations that it examines progress and behaviour over the long-term ring hollow."
Mr Hobby said a shorter notice for inspection would reduce schools' ability to engage with the inspection and may mean senior staff were not in the school for the inspection.