The researchers put dubious tactics down to intense pressure

Academics at Manchester University visited schools serving inner-city or rural areas in 30 local authorities.

They found some schools imported strong teachers to help impress inspectors and heard of weak pupils being sent on work experience during an inspection.

Ofsted said cases of teachers being borrowed by schools to improve their inspection outcome were "very rare".

But Professor Mel Ainscow, who led the research, said he had seen evidence of such practices over five years.

Professor Ainscow said while this would have been unheard of a few years ago, increased pressure on schools - notably government demands for rapid improvement - was taking its toll.

"It's the darker side of pressure. And at times the pressure is having a perverse effect," he said.

And schemes such as Excellence in Cities, which encouraged collaboration between schools, were making these tactics easier, he added.

'Very rare'

A spokeswoman for Ofsted said such cases were very rare.

"Ofsted does not condone any action that seeks to mask weak provision.

"When inspectors become aware that such action has been taken by a school, they investigate the issue and reach appropriate judgements about the school's procedures and effectiveness.

"Under the inspection system, which came into effect in September 2005, schools only receive 2-3 days notice of an inspection, so the chances of giving a false view of a school's provision through borrowing teachers are slim.

"Ofsted also has the right to conduct a school inspection with no notice," she added.

Working together

The Manchester University report, which looked specifically at collaboration between schools, also highlighted positive benefits from schools working together.

"There is evidence from our research that schools can help one another in developing this capacity, by sharing resources, working together to invent new responses and by offering mutual support," the report said.

"In some instances, this can involve quite tangible actions, such as when schools move teachers around to 'fill gaps', or when pupils on the verge of exclusion are offered a fresh start, through managed transfer arrangements between schools."