Parents are damaging children's health and academic prospects by focusing on exams at the expense of sport, according to a campaign backed by Dame Kelly Holmes.
The double Olympic gold medallist said parental pressure to do well in tests was reducing time available for exercise.
She praised teachers for improving sporting opportunities and called on parents to encourage children to be more active.
Dame Kelly, who won the 800m and 1500m at the 2004 games, was speaking to The TES before the launch of the "Be my coach" campaign, aimed at promoting the benefit of sport to parents.
A survey for the Persil-sponsored campaign showed only 21 per cent of teachers said good exam results were the key to success in the workplace with half believing children should focus as much on sport as academic study.
Eight out of 10 thought active children concentrated better in class, and 90 per cent believed children should do more sport outside school.
Yet only 2 per cent of parents played sport with their children every day and a quarter never did.
Dame Kelly, who became the Government's national school sport champion after retiring from athletics last year, said: "When children go home they need inspiration from their parents.
"When I was younger, my mum and dad took me to loads of different sporting clubs like gymnastics, majorettes and martial arts. As I got to about 12 it became athletics.
"Debbie Page, my PE teacher at Hugh Christie school, in Kent, inspired me to get into the cross-country team. I wasn't keen because it was windy and wet but she put me in touch with the local athletics club."
The 575 teachers questioned said sporty children were twice as likely to be confident and have good leadership skills.
Dame Kelly said: "Children say they would do more sport if their parents took it up with them. A few years back there was not enough school sport and it helped create a cotton-wool generation who spent their spare time playing PlayStation. That is now changing."
She urged the Government and local authorities to ensure children in care did not miss out.
"For children in care, sport would give them more direction. Sport can give you a lot of purpose. It would be a key group to work with."
However, the poll, which also surveyed 577 parents and 751 children, found parents lacked confidence.
Almost half (46 per cent) said they were too old, not good enough or that their children would rather play with someone else. Twelve per cent said that they were too tired.
However, three-quarters of children said they would like to play more sport with their parents, with more than half saying they would be less worried about looking silly in front of their friends if they made a mistake.
The campaign, backed by England World Cup star Steven Gerrard, offers free coaching kits for parents on special packs of washing powder.
For details of the campaign and the findings go to www.persilbemycoach.co.uk Information about Kelly Holmes' support for school sport can be found at www.doublegold.co.uk