It’s one of those winter afternoons when the milky light just about survives to the end of the school day. Some 200 well-wrapped people are gathered around a frost-scuffed patch of muddy grass in south-west London, where 30 15-year-old boys are throwing themselves after an oval-shaped ball. Pupils in school scarves and blazers mingle with teachers in overcoats with upturned collars. There are parents too, wearing Barbours and fur, green wellies and tweed caps. “Come on Paul’s,” they cry. “You can do it, boys.”

But the boys of St Paul’s under-15s A team are struggling, their all-white strips drenched from the sodden ground. This is a quarter-final of the national schools rugby cup, entered by more than 500 schools, and St Paul’s is hoping to have a team in the semi-finals for the second time in three years. It’s an impressive record, but then rugby is so much part of school tradition here that they expect nothing less.

Tucked beneath the bend of the River Thames at Barnes, just south of Hammersmith Bridge, St Paul’s is a pound;14,000-a-year independent school for 13 to 18-year-old boys. Academically one of Britain’s top private day schools, it was founded in 1509 at the cathedral of the same name, and gradually migrated west until it found its current, expansive home in 1968.

Rugby and St Paul’s go back a long way, for the school helped found the Rugby Football Union in 1871. One of only two schools involved in setting up the sport’s governing body, St Paul’s has a special role in the game’s history, which means its teams are officially allowed to wear the all-white strip that has since become synonymous with the English national side.

More than a century later, rugby remains a central part of school life. The pitch where this match is dragging to a disappointing close for St Paul’s is one of 12 spread out on either side of the main buildings. St Paul’s runs 18 teams across its five year groups, and there are 10 more at the adjacent St Paul’s preparatory. Some 300 of its 850 pupils play the sport, and more than 20 of its 80-strong staff help run the sides, some of them former top-class players.

Although rugby is just one of 25 sports played here, it is the only one that’s compulsory in the first year. Glen Harrison, a former professional player with Harlequins, and “master in charge of rugby” at the school, explains that teams train for an hour, three lunchtimes a week, and for two hours on “games afternoon”. Matches are held on Saturdays, and sometimes mid-week too, and there’s often a pre-season tour to other rugby-playing countries such as Australia and South Africa.

Perhaps more than any other sport, the history and image of rugby, in England at least, is entwined with schools such as this. Unlike association football, its working-class cousin that emerged from the same privileged bastions of education in the late 19th century, rugby football has remained middle-class, southern, and privately educated. At least, that’s the stereotype. But things are changing.

The England team’s World Cup victory last October may have brought the game to a whole new audience, but the RFU, and its schools section, the English Rugby Football Schools Union (ERFSU), has been trying to spread rugby’s popularity to non-traditional schools since well before Jonny Wilkinson’s last-minute drop kick propelled the sport into thousands of previously rugby-free living rooms.

Ron Tennick, the ERFSU’s national manager, says more than 1,600 of his 3,000 member schools are now state comprehensives, and fewer than 550 are independents. “Rugby has always had the stigma of being an upper middle-class sport. But it’s not now.”

Mr Tennick also takes issue with a Mori survey from November last year that said rugby in schools was dying. “The game in schools is as healthy as it’s been for years,” he says, pointing to the 2,000 schools involved in an “emerging schools programme” for 12 and 13-year-olds, as well as the 800-plus secondaries that take part in national cup competitions.

Mr Tennick, like many in the game, is buoyed by the upsurge of interest generated by the World Cup, but points out that nine of the 15 England players who started in the World Cup final, were educated in state schools.

He says: “More and more specialist sports colleges are playing rugby as one of the five sports they provide, and the number has gone up, especially in the past year, partly as a result of the World Cup. I don’t think we’ll challenge soccer as the national sport, but I’m sure the game will benefit and grow from the massive support the England team had.”

Like St Paul’s, Bow school is an all-boys secondary. It lies just a few miles across the city, but in a different world. Tucked behind Bow Road, half a mile east of Mile End, the school is within easy earshot of the church renowned for its cockney-defining bells. There are no swathes of green playing fields here, just security gates watched over by CCTV cameras, concrete paths, and a playground used as a car park. An 11-16 comprehensive, Bow emerged from “serious weaknesses” in November last year after lifting its A to Cs up to 26 per cent.

Yet, unlikely as it seems, Bow is part of the new image of school rugby and a success story of the RFU’s development programme. When PE teacher Paul Cooper introduced the game six years ago it was a brave move, for this is the East End, where football is king.

“I didn’t want to do football, maybe because everyone else does it,” says Mr Cooper, who put rugby straight on to the PE curriculum. It was “a bit of an eye-opener for the kids”, none of whom had played before, and Mr Cooper took hassle from some parents who, at first, didn’t want their sons to play, largely because they were worried about injuries. “But if it’s taught in the right way, there shouldn’t be any problems, as long as you keep the contact to a minimum and make sure it’s safe,” says Mr Cooper. “I spoke to them, and put pressure on kids to go back and tell their parents they are enjoying it.” Bow is also one of the 2,500 schools covered by insurance through the RFU’s youth trust, which pays a premium of pound;350,000 a year for severe injuries and permanent disability, such as loss of eyes or paraplegia. The RFU also has a charitable fund covering physiotherapy and other care for less serious injuries.

The school has no facilities of its own, so Mr Cooper buses the boys half a mile to a single rugby pitch in Victoria Park, the only one in the London borough of Tower Hamlets.

It took a year, but gradually he won over pupils and parents, established school teams and started playing matches. Bow is the only rugby-playing school in the borough, so the teams travel all over Middlesex and Essex to find opposition. “We took a couple of hammerings at first but we got there gradually,” says Mr Cooper. “The kids here are very talented so they adapted easily.”

Tyson Douglas and his mates Charlie Webb, Ricky Ali and Ragan Bailey were all keen footballers before they went to Bow. Now in Year 11, they’ve been won over by Mr Cooper’s enthusiasm and the physical contact involved. “I’d played football for years,” says Tyson. “But when I started playing rugby I liked the contact side of it. It’s a lot more demanding.”

Two years ago, Mr Cooper and Chris Sigsworth, an RFU development officer for east London, won funding from the New Opportunities Fund to train six Year 10 pupils as rugby coaches. They took two weeks out of the curriculum on work experience, coaching tag rugby (a non-contact version) to pupils at Bow’s feeder primaries. Then they organised a rugby festival and summer camp at Victoria Park, attracting more than 300 children.

Tyson and his friends ran the scheme last summer with the same success, and qualified for community sports leaders awards as a result. This year they’re taking another qualification so Mr Cooper can employ them on future courses. “There aren’t many rugby coaches locally,” he says. “Basically, there’s me on Vicky Park on Saturday mornings, and that’s it.”

For Mr Sigsworth, getting rugby established in other schools like Bow is crucial to the sport’s development, but so are local clubs where youngsters can play when school is over. There’s just one in Tower Hamlets, Millwall Albion on the Isle of Dogs, and it has no youth team. Children play football everywhere, on the hard patches of gravelled asphalt between their blocks of flats. But rugby needs grass, and organisation. Then there’s the culture to overcome. As Mr Cooper puts it, “Kids round here will travel 100 miles to play football, but they wouldn’t leave their front door to play rugby.”

Unless they’re Tyson Douglas. Rugby’s taken such a grip on this 16-year-old’s imagination that it’s become a kind of life-saver. “I don’t even like to think what my life would be like without rugby,” he says. “The only reason I am still in school is because I am playing rugby. That’s the way I channel my energy rather than going into crime.”

Tyson travels across town for an hour and a half once a week to Ealing Common to train with London Wasps’ youth team. Some of St Paul’s pupils play there too, and Tyson is all too aware that he is still stepping on foreign turf. “They have a different attitude,” he says. “We haven’t exactly had an easy life over here, so when I play, I kind of play with my heart. Whereas them, they’re different.

“They get everything they want. They’ve got the boots, they’ve got the dad who will pick them up and drive them there. I have to get the train. Their mums and dads are always there with their Wellingtons and their flask. They bring little sister and the Land Rover. I’m there by myself, struggling to carry my big bag.”

It’s tough, but then rugby’s meant to be a tough sport, and Tyson aims to be a professional, play for England and become the national coach one day.

“I know the ambition seems high but it’s what I want,” he says. Who knows? It really would be a sign that rugby has moved on.

Information on the RFU development programme from 020 8892 2000, www.rfu.com. The English Rugby Football Schools Union is on 01902 380302, www.schoolsrugby.co.uk