Allowing Ofsted inspectors to turn up at schools without notice is simply not "good manners" and could be incredibly disruptive for smaller schools, say headteachers.
Phil Hearne, head of Paddington Academy in London, said it was a simple case of "politeness and manners" to ring ahead when visiting anywhere. He asked what the watchdog was looking to gain with the change.
"I have been through three inspections, each with three days' notice, and that was perfectly reasonable," he said. "It allowed you to gather your thoughts and the paperwork together."
Mark-Andrew Dearden, head of the 80-pupil Quethiock Primary School, near Liskeard, Cornwall, teaches five mornings a week and has no leadership support.
When inspectors called last year giving three days' notice, around a quarter of pupils were out of lessons, sitting national tests.
Mr Dearden said: "If they turn up without calling the night before, they can't expect to have anyone there to meet them. It is impractical and I would need to arrange cover for my lessons." He said the move could also put an end to parents being invited in to give their views to inspectors.
The decision in 2005 to shrink the notice period from two to five days has already resulted in tricky and sometimes distressing situations for schools and heads.
Headteacher Sheila Penny had to postpone her mother's funeral when Ofsted inspectors insisted on visiting Ladybrook Primary in Stockport, Great Manchester, on the same day.
At St Thomas Aquinas RC School in Birmingham, 50 pupils selected for their good behaviour, were bussed back from a Catholic retreat in Stratford-upon-Avon to be present when the inspectors arrived.
And earlier this year, Fairlands Primary in Stevenage, Hertfordshire, suffered a fire that left half of the school unusuable, just two days before inspectors were due.