David Bell is making changes to inspections

From September, schools could be given just two days' notice of an Ofsted inspection, under new rules.

The Chief Inspector of Schools, David Bell, says Ofsted will be 'raising the bar in schools'.

Inspections will be shorter and include more self-evaluation by schools, under changes in the Education Act 2005.

'Right aim'

General secretary of the Secondary Heads Association Dr John Dunford said the new rules were the 'greatest change since Ofsted began'.

Head teachers welcomed many aspects, he said, but warned Ofsted should take the context in which schools were working into consideration.

"Ofsted's aim is right - to carry out inspections in co-operation with the school," Dr Dunford said.

"Generally it's a more grown-up system because it reviews progress over time, rather than just taking a snapshot."

"But by 'raising the bar' as David Bell says, there is the danger of not comparing like with like."

There will be no quotas for the number of schools which will pass or fail Ofsted spokeswoman

Head teachers feared that if more schools failed inspections, parents and the public would conclude that standards were worsening, he said.

From September, schools will be inspected once every three years, instead of every six.

The previous seven-point grading system will be replaced by four points, with schools evaluated as either outstanding, good, satisfactory or inadequate.

Dr Dunford said he understood that more observation would be carried out by senior management in schools.

The inspection team themselves would observe just a few lessons, to verify the school's own evaluation.

"This seems to me to be very sensible," Dr Dunford said, "rather than an inspection team coming in to observe 150 lessons."

However, Dr Dunford also said he hoped inspectors would not concentrate on areas the school acknowledged as weak.

'No quotas'

A spokeswoman for Ofsted said it was not possible to predict how many schools might fail the new inspections.

"There will be no quotas for the number of schools which will pass or fail," she said.

"Ofsted has always had the power to inspect a school without prior warning, but generally two days' notice will be given.

"There may be less notice if the chief inspector of schools has concerns about the school."

"We've been very clear that the new system does involve raising the bar," she added.

"School inspection has developed considerably over the years and schools have developed with this.

"It would be wrong to let improvement stand still."

Dr Dunford said schools were in favour of reducing the notice period of an inspection, to take away anxiety for school staff.

According to newspaper reports, David Bell will change the timing of Ofsted's annual report, moving it forward from next February to October.