Twenty thousand spectators crowd into the century-old Sinhalese Sports Club, Colombo’s answer to Lord’s. All the trappings of big-time international cricket are in evidence - sponsors’ logos, corporate hospitality, a media centre, ball-by-ball radio commentary, a free flow of alcohol and an army of security guards.

There are some Sri Lankan touches too: baila music, massed barracking and exuberant banner-waving. Only this is not a Test or a one-day international match. It is a schools match.

The 120th annual encounter between Royal College and St Thomas’s is the climax of the eight-month Sri Lankan schools cricket season. In comparison, the Test match against India, staged on the same ground a fortnight earlier, was a quiet affair, attracting only 4,000.

Sri Lankan schools cricket is a wonder in world sport, and I doubt whether its popularity can be matched by any other sporting contest between teenagers - anywhere. It is also a unique training ground, emphasising the development of classical cricketing skills, collective discipline and individual flair. From Sri Lankan school playgrounds emerged the remarkable talents which seized the last World Cup, held in south Asia in 1996.

The Royal College v St Thomas’s fixture was the brainchild of the Cambridge Blue-turned-Royal College master Ashley Walker. But in its 120 years, the “Royal Thomian” has evolved way beyond its Eton v Harrow prototype. Today it is only the most glamorous of a host of traditional school rivalries which dot the Sri Lankan cricket calendar.

Among them are St Joseph’s v St Peter’s, played at the Tamil Union Oval, a ground once graced by Australian cricketing legend Don Bradman and one of Colombo’s four Test match venues. “The Battle of the Maroons” is fought between Ananda (where batsman Arjuna Ranatunga first learned the art of captaincy) and Nalanda. And in war-torn Jaffna, St John’s has somehow sustained its long-established rivalry with Hindu College, under the heavily armed aegis of the Tamil Tigers and the government .

All are traditional two-innings games, a form rarely played in British schools these days, and are extensively covered in the Sri Lankan media. Until 1987 all school matches were friendlies but now the old rivalries have been incorporated into modern competitive structures. Now schools compete for the Coca Cola Bottlers’ Trophy and the multi-division Elephant Lemonade Cup, not to mention the Horlick’s Trophy two-day under-13 competition. Meanwhile, individual school cricketers compete in newspaper polls for the most popular schoolboy cricketer of the year.

Sri Lanka remains the last outpost of the Victorian public school ideology of cricket. It may be the only place in the world where you can still find people quoting Tom Brown’s Schooldays or Henry Newbolt’s Vita Lampada (“play up, play up, and play the game”) read without a trace of irony.

In a brochure commemorating a recent match between Ananda and Nalanda, the Nalanda principal waxed lyrical: “Cricket is universally recognised as a gentlemen’s game. It helps students to cultivate patience, love and obedience to their leaders. It is not performed to find a winner but to appreciate the finer strokes of the game in a very fascinating manner which gives thrilling sensation to spectators.”

Sri Lankan schools cricket is not without its dissidents, and many who have passed through the island’s educational system have bitter memories. In Shyam Selvadurai’s Funny Boy, a touching and observant novel set in Colombo during the years leading up to the anti-Tamil pogrom of 1983, the gay Tamil protagonist attends a school clearly modelled on St Thomas’s, where he is compelled to memorise Vita Lampada. To him, the poem “spoke of a reality I didn’t understand. Cricket here consisted of trying to make it on the first 11 team by any means, often by cheating and fawning over the cricket master. Cricket was anything but honest.”

After this year’s Royal Thomian I was taken to the venerable Orient club by a friend who is a cricket fan but also a severe critic of the complacencies of the Sri Lankan elite. There we met one of the island’s best known editors, so drunk after three days at the Royal Thomian that he was incapable of putting verbs and nouns in any decipherable order. My friend shook his head sadly and observed: “Now you see what schools cricket has done to the Sri Lankan intelligentsia.”

Still, it’s given us world-class players the likes of Ranatunga, Jayasuriya and Aravinda de Silva - and for cricket fans that will be enough.

Mike Marqusee is the author of ‘War Minus the Shooting, a journey through south Asia during cricket’s World Cup’ (Heinemann), and the forthcoming ‘Redemption Song: Muhammad Ali and the spirit of the Sixties’ (Verso)