The increasing use of private tutors among affluent families is distorting the results of school league tables, head teachers warned.

Allegations that the Blairs have hired to services of private tutors for their two eldest sons, Nicholas and Euan, have highlighted the fact that more and more parents are using tutors to get the best results possible.

We're not really sure what league tables are measuring if a third of the country are sending their children off for tutoring

Sylvia Morris, primary head

It is estimated that in some schools in privileged areas, up to 65% of pupils may be receiving private coaching.

Now head teachers warn that if a significant number of children are being given extra one-to-one help, leagues tables - which are based on national exams and tests such as SATs and GCSEs - are misleading.

"The question of private tuition further illustrates the failure of league tables to portray accurately the performance of schools," said John Dunford, general secretary of the Secondary Heads Association.

Growing pressure

Sylvia Morris, head of the Cathedral Primary School in Southwark, London, said she was aware that a number of parents - though not in her own school which serves a deprived area - were turning to private tutors.

"I have a number of colleagues who are themselves becoming increasingly concerned because the pressure on primary pupils becomes greater," said Ms Morris.

"And parents begin to say it's because of we've had them privately tutored that they've got through the SATs, not because of the school and it can undermine some of the good work school are doing."

One-to-one

Ms Morris said results at her school would go "through the roof" if teachers were able to give them that little bit extra, as a private tutor would.

"It would be wonderful, wouldn't it, if we all had the opportunity in school to have one teacher to one pupil for one hour a week?

"Wouldn't that be much better than the pressure the children are under outside of school?"

But while middle-class parents were able to afford the fees of private tuition, children and schools in less privileged areas would continue to lose out in terms of rankings in the league tables.

"It's distorting league tables because it becomes more difficult to actually measure whether those league tables are a measure of the performance of the schools or whether it's a measure of the number of parents who get their children privately tutored in order to get the best results," said Ms Morris.

"So we're not really sure what those league tables are measuring if a third of the country are sending their children off for tutoring during the primary phase."