Children as young as eight are being tutored to pass the 11-plus as competition for grammar school places increases. But many struggle when they arrive and the experience can be damaging, say leading headteachers.
Experts also say "over-tutoring" does not significantly help. The warnings follow a TES investigation which found that parents are spending up to Pounds 1,500-a-year on personal tutors to get their children into the 164 surviving grammar schools. These schools admit to receiving on average five applications for every place.
Headteachers warned this week that the practice could be damaging children's confidence and risks undermining academic performance later in their school life.
Dr Mike Walker, headmaster of King Edward VI grammar in Chelmsford, Essex, said: "The nature of 11-plus type exams requires accuracy at speed, and with unpredictable questions, tutoring can only teach familiarity and technique. What is fundamentally important is what's appropriate for an individual.
"If a child is tutored above their natural level of capability for any exam then they could have a miserable time on joining the school."
The Grammar School Association estimates that 75,000 children annually sit the 11-plus for only 20,000 places. Its chairman Brian Wills-Pope said:
"Children should not be pushed beyond their natural ability to pass the 11-plus. If they are over-tutored then there is a chance they may become unhappy during their subsequent seven years at school."
In 2002, a study by Professor Diane Reay, of King's College, London, examined the choices available to 454 inner-city primary school pupils. It said that in some schools more than half of 11-year-olds had at least 18 months of private tuition in English and maths before they sat the 11-plus.
But experts said this week that, with a recent explosion in the number of internet sites offering examination coaching, that number could now be much higher.
A private tutor in London, who asked not to be named, said: "More than half of my pupils are aged 10 and 11 but there is a definite rise in the trend to tutor from a much younger age.
"I have children aged eight and nine coming weekly."
The mother of a nine-year-old girl defended her choice to seek a private tutor two years before her daughter will sit the 11-plus. "Competition is so high and it's all about getting our children places at better universities, and to get better jobs," she said. "I suppose it's determination at any cost."
Another parent from Kent, where there are 45 grammar schools, said: "I'm not a pushy parent but my son is extremely academic. He really wants to go to the local grammar school but his tutor has made it clear how he's being marked against children who have been tutored for 18 months.
"I know tutoring goes on, but I had no idea parents were generally this focused and aggressive. It's just not a level playing field out there."
Liz Lee, executive member of the Campaign for State Education, said:
"Grammar schools simply perpetuate a two-tier education system in which your child can have a perceived better education, but only if you can pay enough to get them tutored through the 11-plus. We believe in providing the best possible education for every child, not just those who can afford the best tutors."
A study by Bristol university in 2004 showed that children from disadvantaged backgrounds are less likely to go to grammar schools than their more affluent peers, even if they are just as clever.
In the 19 counties where significant selection remains, just 2 per cent of pupils attending grammar schools are entitled to free school meals, compared with 12 per cent at other secondaries in those areas.