One in four parents pays for private tuition to boost their children's grades - but many are wasting their money, a study reveals today.
Pupils who have private tuition achieve on average just half a grade higher in their maths and English GCSEs than those who have had no extra tuition, research from London university's institute of education shows.
Academics found boys increased their performance by three-quarters of a grade in maths, often sufficient to push them up a grade.
But maths tuition was shown to have little effect on girls' performance.
There was no evidence that out-of-school coaching in English had any effect on GCSE grades, for either boys or girls. Twenty-seven per cent of the 300 Year 11 pupils surveyed by academics admitted using a private tutor at some point during their schooling, usually in maths or English.
The study's authors suggested that a lack of confidence among the girls led them to seek coaching when in fact their grades did not need to be improved. A general improvement in girls' performance between Years 9 and 11 also makes it more difficult for tutors to boost results.
Judy Ireson, professor of psychology in education and author of the report, said previous research showed coaching offered by schools raised grades.
"Most people assume tutoring is the answer to boosting children's attainment," she said. "But there is no regulation of private tutors, so there is no guarantee that the tutor you get is going to be good."
The Prime Minister is among many parents who believe private tuition, which costs on average pound;20 an hour, reaps benefits. Tony Blair hired teachers from Westminster school, one of the UK's highest-achieving private schools, to tutor his eldest children.
Rashmikant Shah, from Portsmouth, has employed an English tutor for his 15-year-old daughter, Anjlee, since primary school. Last year, she sat English literature and language GCSEs, achieving As in both.
"The education level at her school is very high, but private tuition backs her up," Mr Shah said. "It gives her a head start, puts her above the other students."
Robert Breslin, maths teacher at Holloway school, north London, thinks tuition can reinforce classroom teaching.
He said: "If you go over something again and again, it's more likely to stick. It does not matter if the tutor teaches a different method: if you have more tools, it is only going to help you."
Other teachers were less enthusiastic. Chrissie Yates, head of English at Darton high, in Barnsley, said she would be insulted if pupils hired a tutor.
"It is a sign a department is not doing what it should," she said. "They are not willing to put their trust in the school."
Sharon Ebbs, head of maths at an Essex comprehensive, said: "You cannot guarantee tutors do not help with GCSE coursework, which is cheating. You should not benefit just because you have the money to pay for it."
Clive West, the director of private-tuition agency Anysubject, said: "There can be good and bad teachers in schools. Parents are not dim-witted. They do not come back to us without reason."
Mapping and evaluating shadow education, by Judith Ireson and Katie Rushforth, is available on: www.ioe.ac.uk
'I WANT TO BUILD MY CONFIDENCE'
Tiffany Walker prefers to go to a private tutor even though extra maths coaching is available at school during the lunch break.
The 14-year-old pupil at Wavell school, in Hampshire, is seeing a Pounds 23-an-hour tutor, in the hope of improving her maths Sats result.
"I want to build my confidence, so I can get my exam level up," she said.
"There are people in school you can go to at lunchtime. But I have netball then."
Her mother, Jill, said: "I am not a pushy parent. I just want her to feel happier going into the exam, and more confident answering the questions."
Tiffany is happy to face an additional hour of schoolwork every week and does not think her friends will call her a swot. Neither does she believe her teachers will mind. "It's a sign that I want to do well."