Tennis: In the last 25 years the Nick Bollettieri Tennis Academy has become the most reliable production line in tennis. Paul Kelso looks at the career and philosophy of the controversia coach.

This morning, as every morning at the Nick Bollettieri Tennis Academy in Florida, around a dozen of the most promising young tennis players in the world - accompanied by several hundred more who simply have the most ambitious and richest parents - will be beating balls back and forth in the sunshine. It is the same every day, nine months of the year on the sprawling 45-acre complex in the Tampa suburb of Bradenton, but today there should be an extra zip to the groundstrokes traded by the players, some of whom are barely taller than the rackets they wield.

Last Saturday, in one of the most charming and unexpected sporting upsets of the year, 17-year-old Russian Maria Sharapova defeated Serena Williams to win the women's singles final at Wimbledon. The following day 16-year-old Miles Kasiri finished as runner-up in the boys' singles, the best finish in the event by a Briton since 1972 and a result interpreted as an augury of better times ahead for British tennis.

Both Sharapova and Kasiri honed their games at the Bollettieri academy, and Sharapova made a point of thanking her coach in her centre-court acceptance speech. Today her success and that of Kasiri will be used to motivate the latest crop of young talent passing through the most famous, successful and controversial tennis school in the world.

Many elements make up a champion athlete, but in tennis one of the surest ways to the top appears to be spending a spell at the academy founded in 1978 by the perma-tanned former paratrooper, whose pearly-white grin has widened with every champion. Sharapova joins a list of grand slam-winning Bollettieri graduates that includes Andre Agassi, Jim Courier, Monica Seles and Mary Pierce.

Sharapova arrived at Bradenton aged just seven, following a recommendation from Martina Navratilova. Bollettieri agreed the young Sharapova had a rare talent, and she was quickly subsumed into a regime that has earned a reputation as the toughest youth academy in professional sport. Some have compared it to boot camp - it has been described as Alcatraz-on-Sea - and others questioned the effect of a hyper-competitive atmosphere on fragile adolescents, but there is no question that in the last 25 years the Bollettieri academy has become the most reliable production line in tennis.

Born in North Pelham, New York State, Bollettieri played American football, baseball and basketball in his youth, but the individual game quickly became his passion. Showing a realism he tries to coach into his charges today, he quickly realised, however, his talent was limited.

"I may not have known much about the game, but I knew enough to realise I was not going to be the first great Italian-American tennis player," he wrote in his autobiography, My Aces, My Faults. He was to become perhaps its greatest coach, however, and after serving as a paratrooper in Asia he pursued a career in the game, initially as a jobbing coach working across the Americas from Wisconsin to Puerto Rico.

It was a trip to a purpose-built tennis centre in California in the mid-1970s that helped decide his fate. In 1978 he borrowed $1 million from a friend, built courts, bought an old motel that was to be the first dormitory for his charges, co-opted a local private school to accept his pupils for academic work, and opened his tennis school.

Nearly 30 years on, the academy is unrecognisable from those ad-hoc beginnings. In 1987 IMG, the leading sports promotion and athlete management company in the world, bought into the facility, using it to develop highly marketable stars. Golf, basketball, soccer and American football academies have been founded based on the tennis academy, all of them supported by a performance institute and a "mental conditioning" centre. Around 575 kids enter the full-time programme every year, five per cent of whom will be earmarked for progress to the professional ranks. Of the rest, most will make their way to college with a well-drilled forehand to offset the disappointment of their parents.

In the manner of modern American gurus, Bollettieri has a creed (literally; the Bollettieri Creed is constantly referred to in the academy's literature and on its website). "Our programme is based on three guiding principles: Discipline, Responsibility and Effort," he says.

Translated, this means hard work and lots of it. Bradenton operates on a boarding-school basis, with a nine-month year combining four hours of study a day with five hours of intensive tennis drills that produce supremely fit, focused and disciplined athletes. For the select few, the Sharapovas and Agassis, a scholarship is provided; annual fees of more than $40,000 ensure that the others are made up exclusively of children of the affluent.

"From the very start we stressed hard work and fitness," says Ted Meekma, a co-director of the academy and Bollettieri's business partner for the last 30 years. "We got the kids up at 6.30 a.m., ran, did push-ups, sit-ups and hit a lot of balls. We drill them hard, and it pays off . . . Everything we do here is designed to help these kids cope with the mental and physical demands of competition."

Bollettieri's fierce physical regime and emphasis on strength and power were apparent on Saturday as Sharapova blasted the supremely-conditioned Williams off the centre court. It is an approach that has brought results, but also led to criticism that "Bollettieri players" are one-dimensional grinders, relying on weighty groundstrokes blasted from the baselines over the more delicate instinctive skills honed at the net. Agassi and Courier won their titles from the back of the court, striking their returns earlier than had previously seemed possible and relying on exceptional fitness, and in Agassi's case speed, to outdo their opponents. It was a hugely effective and influential approach, so much so that true serve-volleyers such as Tim Henman, or genuine "all-court" touch players like Wimbledon champion Roger Federer, are now the exception. Meekma, however, rejects the suggestion Bollettieri players lack inspiration.

"You could not say Andre or Jim were defensive. Nick coaches people never to take a backward step, but he also makes them play to their strengths. When someone returns the ball like Andre, you would not coach him to charge to the net . . . \ can spot an idiosyncrasy that could come back to limit a player, and he gets rid of it, which helps them fulfil their potential."

That talent manifested itself in the case of Agassi when Bollettieri set about harnessing the young Las Vegan's extraordinary hand-eye co-ordination. Realising his charge was able to react to his opponent's shots faster and more decisively than any player he had ever coached, he encouraged Agassi to stand two yards inside the baseline to take returns. Constant drilling produced perhaps the most devastating returner of serve the men's game has ever seen.

Bollettieri's other demonstrable talent is in self-promotion. "Nick has always grasped the fact for this to work we have to promote the business and the athletes," explains Meekma. "It has to be a commercial enterprise as well as a coaching academy. If the business isn't working then we can't afford to pay for the Monicas and Andres and Marias to pass through and make it to the top."

Writing in Monday's English Independent, the coach was in no doubt who should take the credit for Kasiri's run to the final: "Let's get one thing straight. It wasn't a success story for English tennis that Kasiri reached the final. It was another success for the IMG Bollettieri Academy. Because when it came to the crunch a few years ago . . . it was us who stepped up to the plate and gave him his chance, a scholarship at the academy."

Neither was Bollettieri slow to take credit for Sharapova's success: "I was delighted and overwhelmed when Maria thanked me by name for being so important in her career. Some people quickly forget those who have helped them achieve their goals. Not Maria."

This last tart remark may well be a veiled reference to criticism he has received from former pupils including Agassi, who has sought to play down Bollettieri's influence on his career, and Seles, with whom he fell out. He has also been described as "insignificant" by John McEnroe, and by common consent his relationship with Boris Becker was of little benefit to either man.

The fact Bollettieri took credit for Kasiri's success caused huge annoyance at the UK's Lawn Tennis Association, the much maligned governing body of British tennis responsible for developing successors to Henman. David Felgate, Henman's former coach and now director of performance at the LTA, described it as "rubbish". He does acknowledge the Floridian's record, however.

"Nick Bollettieri has had success over many years and that breeds success," he says. "With a reputation like that he has the pick of the best players in the world coming to him. In Britain we are dealing with kids from a single country, but the principles are the same. You provide great coaching, a high level of competition and make sure you work with the best. His success is a useful stick to beat the LTA with, but you never hear about Bollettieri's failures. And at the end of the day, I don't care where our kids come from as long as they win."

Unfortunately for the LTA, comparisons with the American are not about to go away. Even at 72, Bollettieri rises at 5 a.m. six days a week to exercise, skis and play golf, and his enthusiasm for a game he has profoundly influenced shows no sign of diminishing. "I just love excitement and being with kids and around sports," he has said. "It's being able to make an impact on people's lives. How could you ask for anything more than that?"

ANDRE AGASSI - Joined the Bollettieri tennis academy as a 13-year-old in 1983 and turned professional three years later. Won his first tour title at Itaparica in 1987. Nurtured in his earlier years by his father, who boxed for Iran in the 1948 and 1952 Olympics, before emigrating to Chicago. Won 58 singles events, including 16 Masters Series and eight grand slam titles.

JIM COURIER - Born in Florida in 1970, he excelled at baseball but chose to concentrate on tennis as a career. Was enrolled at the Bollettieri academy between 1983 and 1990, turning professional in 1988. Won his first grand slam event at the French Open in 1991. Won the French Open once more and the Australian Open twice.

MONICA SELES - Born in Novi Sad, in the province of Vojvodina in the northern part of Yugoslavia, in 1973, she was encouraged to play tennis by her father, who trained her in the town's potholed parking lot. Arrived at the Bollettieri academy in 1985, aged 12. At 17, she became the youngest top-ranked tennis pro in history. Went on to win nine grand slam titles.

ANNA KOURNIKOVA - Born in Russia in 1981 and sent to the Bollettieri academy at the age of 10. Reached the Wimbledon semi-final weeks after her 16th birthday, but has yet to win a major tournament.

MARY PIERCE - Born in 1975 in Montreal, Canada. Turned professional at the age of 14 and spent a number of years under the tutelage of Bollettieri.

Her split with him was the subject of intense media speculation and their professional relationship was eventually to end on a sour note. Winner of two grand slams and 15 other tournaments during her career.