State school pupils are being denied competitive sport because it isn't a priority for headteachers.
The schools inspector Ofsted found just 13 per cent of comprehensives expect their pupils to compete on the playing field and regarded sport as 'an optional extra'.
It said that is the main reason why England's rugby and cricket teams are full of ex-private school pupils – a rationale condemned as 'ridiculous' by a teachers' union.
The watchdog launched its probe into the state of school sport after Team GB's success at London 2012.
It found 'unacceptable discrepancies' between the number of pupils attending state schools and playing top-level sport.
Those with a private school background make up most of the players in rugby union's Premiership and more than a third of top cricketers.
That is despite private schools educating just seven per cent of school pupils.
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Ofsted boss Sir Michael Wilshaw said state schools were failing kids and causing 'social inequality' between rich and poor youngsters.
He also insisted that pupils who play lots of sport also do well academically.
Sir Michael said: "It simply cannot be right that state educated athletes are so woefully under-represented in our elite sports.
"There is no reason why more pupils from state funded schools can't be batting for England at the Ashes or scoring a winning try in the next Six Nations."
But teachers' leaders condemned the report.
NUT deputy general secretary Kevin Courtney said: "Ofsted's comparison between state and independent school sport provision is ridiculous.
"It is not teachers who are the barrier to a good sports education in schools but a lack of support, resources, funding and facilities.
"Those are the areas Ofsted should have been looking into."
John Steele, chief executive of the Youth Sport Trust, said: "This report should be a wake-up call for those schools that do not fully value sport's place in school life."
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