Children from two preparatory schools were being kept at home today amid fears about the Sars virus.

But teachers at Terrington Hall and Woodleigh School, both in the Malton area of North Yorkshire, played down the significance of the move, saying only a small number of children were involved and the parents had every right to take whatever action they wanted.

Both schools have seen students return from Hong Kong this week following the Easter break and both have decided against quarantine measures seen in other establishments.

The headteachers said today that they were acting in accordance with all available professional advice. Michael England, the head of the 210-pupil Woodleigh School, at Langton, said between five and 10 per cent of children were being kept at home by their parents.

He said the eight students who had returned from the Far East were being checked twice a day as well as having been screened both before and after their flights.

Mr England said: ''We are following all the available professional advice which is completely consistent. ''We are doing what the World Health Organisation advises.''

He added: ''But I am not going to criticise the parents who have kept their children a home. ''It is their prerogative. They are fully entitled to take that decision.''

The head of 208-pupil Terrington Hall, Jonathan Glen, confirmed about a dozen children from five families were being kept away, but said most of these were from the pre-school.

Mr Glen said: ''The suggestion that there is any kind of hysteria or anything like that is just not true. Only one of the children involved is from Years six, seven and eight with our Chinese Hong Kong students.''

He added: ''I have told the parents 'I disagree with your decision but I defend for ever your right to make it'.'' Mr Glen said the children who had returned from Hong Kong had been quarantined while at home. He said none of the children staying at home were boarders.

The action of the two schools contrasts with some other private boarding schools which have decided to quarantine pupils returning from the Far East.

At another North Yorkshire school, Harrogate Ladies College, headteacher Dr Margaret Hustler has volunteered to join 42 pupils in isolation in a boarding house.

It came as a medical academic today said the Government should clear up the confusion and student disruption caused by British schools' differing policies on Sars.

Officials should urgently develop a common policy for Sars for schools said Ian Wong, director of the Centre for Paediatric Pharmacy Research at the University of London.

In a letter published in the British Medical Journal, Mr Wong said schools were advising parents differently over the issue.

Chinese pupils' schooling was being disrupted because schools were imposing quarantines, he wrote.

Yet advice from the Health Protection Agency said that there was no need for students returning from Sars-affected areas to be excluded or quarantined unless they were unwell.

Mr Wong used the Internet to identify 10 schools' Sars policies and found five following HPA guidelines, four issuing a 10-day quarantine and one advising students not to return for the summer term until the virus was understood to be contained.

He wrote: ''The situation looks confusing. I urge the Department of Education and Skills and the Department of Health to work together in his matter urgently and develop a common policy for schools.

''This will assist schools in making rational decisions and more importantly address the fears of parents and children.''