But the Department for Education and Employment insisted there had been a mistake. And it says in a letter to the father that because a number of other schools have made similar errors, the department will be improving its guidance on special educational needs pupils.

The case of Christopher Diedo of Dartford, Kent, highlights the delicate issue of whether children with special educational needs should be included in school performance tables. Children’s rights groups are concerned that some schools are reluctant to admit such pupils. Headteachers have been lobbying for the results of statemented children to be omitted from the tables.

The results for St Anselm’s Roman Catholic primary school in Dartford have been corrected so that it now has to share top place in the local tables for 11-year-olds with Fawkham CofE School.

Andrew Diedo, a retired drama, media and special needs teacher, said: “When Christopher took the tests, he secured a double ‘W’ (working towards level 1) for English, a double ‘W’ for maths and level 1 in science. I am very proud of his achievements.”

Mr Diedo believes 11-year-old Christopher may be the first child with Down’s Syndrome on the full-time roll of a mainstream secondary in the London borough of Bexley. He says his son has settled into St Columbus Roman Catholic grant-maintained secondary school well.

Mr Diedo claims that St Anselm’s, where Christopher was the only statemented pupil, did not want his son on its roll, although the parents and pupils at the school had always accepted him as “equal worth”.

He says the outreach consultant teacher, who administered his son’s key stage 2 national tests, gave the results to the school and explained that they had to be recorded on the return sheet for those children sitting the KS2 tests.

Allan Short, of the parental choice division at the DFEE, in a letter to Mr Diedo, wrote: “I understand that, initially, a decision was made that Christopher should remain on the roll of St Anselm’s school until the age of 14.

“In those circumstances, he would reach the end of KS2 at age 14 and be assessed then, prior to leaving school.

“A decision was made later, however, that Christopher should transfer to secondary school at the start of the current school year.

“As a result, he became eligible for assessment in 1995-96. I understand that Christopher’s phased transfer during the school year from Year 3 to Year 6, together with the confusion over his status as an eligible pupil, led to the failure to recognise Christopher’s results as those of an eligible pupil and to pass them to the department.”

Mr Diedo says the school was in no doubt about when his son was leaving. He is angry that the DFEE will not discipline the school and is concerned that other schools might deliberately omit the results of statemented pupils.

A statement issued by Bernadette King, St Anselm’s headteacher, says: “We have accepted that Christopher Diedo’s results were not included in the published league tables for our school. We genuinely believed we did not have to record Christopher’s results. The DFEE stated that as this was the first year of the published results, we were not the only school to make this error.”

The National Association of Head Teachers, in a letter to the DFEE, criticised the inclusion of pupils with statements in the league tables. The vast majority of these pupils will struggle to achieve level 4, it says.