When you have a teenager on the rampage, who are you going to turn to? In America, parents send their troubled offspring to Jamaica's Tranquility Bay - a 'behaviour-modification centre' which charges $40,000 a year to 'cure' them. Decca Aitkenhead, the first journalist to gain access to the centre in five years, wonders if there isn't too high a price to pay

Were you to glance up from the deserted beach below, you might mistake Tranquility Bay for a rather exclusive hotel. The statuesque white property stands all alone on a sandy curve of southern Jamaica, feathered by palm trees, gazing out across the Caribbean Sea. You would have to look closer to see the guards at the wall. Inside, 250 foreign children are locked up. Almost all are American, but though kept prisoner, they were not sent here by a court of law. Their parents paid to have them kidnapped and flown here against their will, to be incarcerated for up to three years, sometimes even longer. They will not be released until they are judged to be respectful, polite and obedient enough to rejoin their families.

Parents sign a legal contract with Tranquility Bay granting 49 per cent custody rights. It permits the Jamaican staff, whose qualifications are not required to exceed a high-school education, to use whatever physical force they feel necessary to control their child. The contract also waives Tranquility's liability for harm that should befall a child in its care. The cost of sending a child here ranges from $25,000 to $40,000 a year.

Opened in 1997, Tranquility Bay is not a boot camp or a boarding school but a 'behaviour modification centre' for 11- to 18-year-olds. An American Time magazine journalist visited in 1998, and since then no media have been allowed inside. With all access denied, there has been little coverage beyond sketchy reports based on hearsay - even the local community knows almost nothing of what goes on. My discovery of Tranquility Bay came only by accident in 2000, while living nearby, and all my approaches since then were, like every other media request, firmly rejected.

The owner is an American called Jay Kay. He doesn't trust the media, because 'they go for sensationalist stuff. Nothing has really presented things in a way that is factual.' On the other hand, he believes anyone who saw inside Tranquility would support and admire it, and blames criticism on ignorance. So Kay has been in a dilemma. His business is expanding, and he is turning his attention to the UK, for he believes there is a large untapped market of British parents who would ship their children straight off to Jamaica if only they knew about Tranquility. The British government, too, he hopes, might send him children in its care. 'If social services was interested, at $2,400 a month I bet they can't offer our services for that.'

This spring he decided to grant me and a photographer unprecedented, exclusive access. If he didn't like the result, 'Hell will freeze over before anyone gets in here again.'

The first impression once inside Tranquility Bay's perimeter walls is of disconcerting quiet. Students are moved around the property in silence by guards in single file, 3ft apart - a complicated operation, because girls and boys must be kept segregated at all times, forbidden to look at one another.

Tranquility has a language of its own. The vocabulary is recognisable, but its use has been delicately customised, so that boys are 'males', girls 'females', and they are all divided into single-sex 'families' of about 20. The families have names such as Dignity, Triumph and Wisdom, and are led by a staff member known as the 'family mother' or 'father', addressed by the children as Mum or Dad. The 200 staff are all Jamaican.

Along with multiple guards known as 'chaperones', the family mothers and fathers control and scrutinise their children 24 hours a day. The only moment a student is alone is in a toilet cubicle; but a chaperone is standing right outside the door, and knows what he or she went in to do, because when students raise their hand for permission to go, they must hold up one finger for 'a number one', and two for 'a number two'.

Corporal punishment is not practised, but staff administer 'restraint'. Officially it is deployed as the name suggests, to subdue a student who is out of control. However, former students say it is issued more often as a punishment. One explains: 'It's a completely degrading, painful experience. You could get it for raising your voice or pointing your finger. You know you're going to get it when three Jamaicans walk in and say, "Take off your watch." They pin you down in a five-point formation and that's when they start twisting and pulling your limbs, grinding your ankles.'

Before sending their teen to Tranquility, parents are advised that it might be prudent to keep their plan a secret, and employ an approved escort service to break the news. The first most teenagers hear of Tranquility is therefore when they are woken from their beds at home at 4am by guards, who place them in a van, handcuffed if necessary, drive them to an airport and fly them to Jamaica. The child will not be allowed to speak to his or her parents for up to six months, or see them for up to a year.

Let us say you are a new female assigned to Challenger family. You sleep with your family in one bare room, on beds which are pieces of wood on hinges hung on the walls. The day begins with a chaperone shouting at you to get up. You put on your uniform and flip-flops (harder to run away in) in silence and fold your bed against the wall. The room is now completely bare. After performing chores, the family is ordered to line up, for your family mother to do a head count.

You are walked to a classroom to watch an 'EG' - a 30-minute video intended to promote 'emotional growth' - on a theme such as why you shouldn't smoke. Then the family is lined up, counted and walked to the canteen to eat a plate of boiled cabbage and fish in silence while listening to an 'inspirational tape' broadcast loudly through the room, urging you to, for example, eat healthily.

'If 70-80 per cent of the food you eat is not water rich, what you are doing is clogging your body. Eat 80 per cent water-rich food. Try it for the next 10 days. Watch what happens to your body. It will blow your mind.' Students have no choice in what they eat - there is a seven-day plan of basic Jamaican meals which never changes, and eating less than 50 per cent of any dish is forbidden.

Morning routines vary between families. Some shower (three minutes, cold water), others wash clothes (outside, in buckets, cold water), or exercise (walk round the yard). At 9.30am, each family is moved into a classroom for two hours. You continue the US high-school curriculum where you left off at home, but there is no teaching.

Watched by chaperones, you read prescribed course books, take notes, then sit a test after each chapter. Two or three Jamaican teachers sit at the back of the room in case you get stuck, and they may be able to help. But to mark the tests, they have to use an answer key sent down from the States.

After lunch and another inspirational tape come three further hours of school, a second EG, plus an educational video about a historical figure of note. There is a sports period, a family meeting, a final meal with tape, followed by a period called Reflections, when you must write down what you have memorised from the tapes and EGs. You may also write home to your parents, and though staff can read your mail, you may write what you like. But Tranquility's handbook for parents warns them not to believe anything that sounds like a 'manipulation', the programme's word for a complaint.

There is no free time, and you are never alone. At 10pm everyone is in bed for Shut Down; the lights go off, and Tranquility is silent, save for waves crashing on to the beach below. Chaperones watch you through the night. And the next day is exactly the same. As is the next, and the next.

'Yep, identical,' says Kay. 'Exactly identical. Now you see,' he adds, with a grim nod of satisfaction, 'why kids are not happy here.'

Tranquility Bay is one of 11 facilities affiliated to an organisation in Utah called the World Wide Association of Speciality Programs. The facilities are located in the States and Caribbean region, and although independently owned, all run the same programme, devised by Wwasp.

Jay Kay is 33 years old, and the son of Wwasp's chief director. He opened the facility at the age of 27, after four years as administrator of a Wwasp-run juvenile psychiatric hospital in Utah. Previously he had been a night guard there, and before that a petrol-pump attendant, having dropped out of college. He has no qualifications in child development, but considers this unimportant.

'Experience in this job is better than any degree. Am I an educational expert? No. But I know how to hire people to get the job done.' There is more than a touch of the Jerry Springer guest about his looks - heavy, shaven-headed, colourless, and a similarly deadening certainty of mind. 'I've got the best job in the world,' he claims, but he carries himself like a man who has learnt to expect the worst, and is seldom disappointed.

Tranquility is basically a private detention camp. But it differs in one important respect. When courts jail a juvenile, he has a fixed sentence and may think what he likes while serving it, whereas no child arrives at Tranquility with a release date. Students are judged ready to leave only when they have demonstrated a sincere belief that they deserved to be sent here, and that the programme has, in fact, saved their life. They must renounce their old self, espouse the programme's belief system, display gratitude for their salvation, and police fellow students who resist.

A finely engineered reward-and-punishment system has been designed to effect this change. In order to graduate, students must advance from level 1 to 6, which they do by earning points. Every aspect of their conduct is graded daily and as their score accumulates, they climb through the levels and acquire privileges.

On level 1, students are forbidden to speak, stand up, sit down or move without permission. When they have earnt enough points to reach level 2, they may speak without permission; on level 3, they are granted a (staff-monitored) phone call home. Levels 4, 5 and 6 enjoy significantly higher status. In addition to enjoying privileges, such as (strictly limited and approved) clothing, jewellery, music and snacks, they are employed for three days a week as a member of staff, and must discipline other students by issuing 'consequences'.

Every time a member of staff or upper-level student feels a student has broken a rule, they 'consequence' them by deducting points. Rule-breaking is classified into categories of offence. A 'Cat 1' offence, ie rolling your eyes, is consequenced by a modest loss of points. A 'Cat 3' offence, eg swearing, costs a significant number, and may drop the student's score beneath their current level's threshold, thus demoting them and removing privileges.

'You know,' offers Kay, 'if people want to talk about the length of the programme, it's up to the child. If a parent wonders why their kid is here so long, well gee, we are doing our part, maybe you need to ask your little Joey why he is not moving forward. Everyone knows how to earn the points.'

The strategy of coercing children to rewire themselves is the concept Kay is most proud of, for he believes it places troubled teenagers' redemption in their own hands. The choice is theirs.

'For years, we just believed if you make the kids do what you want them to do, then they will make the change. But what we figured out was, why not get them to come to the conclusion that they need to make the change themselves? That's what makes this programme special. It's up to them.'

Students who fail to grasp this formula are forcefully encouraged to get the message. One girl currently has to wear a sign around her neck at all times, which reads: 'I've been in this programme for three years, and I am still pulling crap.'

When most children first arrive they find it difficult to believe that they have no alternative but to submit. In shock, frightened and angry, many simply refuse to obey. This is when they discover the alternative. Guards take them (if necessary by force) to a small bare room and make them (again by force if necessary) lie flat on their face, arms by their sides, on the tiled floor. Watched by a guard, they must remain lying face down, forbidden to speak or move a muscle except for 10 minutes every hour, when they may sit up and stretch before resuming the position. Modest meals are brought to them, and at night they sleep on the floor of the corridor outside under electric light and the gaze of a guard. At dawn they resume the position.

This is known officially as being 'in OP' - Observation Placement - and more casually as 'lying on your face'. Any level student can be sent to OP, and it automatically demotes them to level 1 and zero points. Every 24 hours, students in OP are reviewed by staff, and only sincere and unconditional contrition will earn their release. If they are unrepentant? 'Well, they get another 24 hours.'

One boy told me he'd spent six months in OP.

I didn't think this could be true, but it transpired this was not even exceptional. 'Oh no,' says Kay. 'The record is actually held by a female.' On and off, she spent 18 months lying on her face.

'The purpose of observation,' Kay offers, 'is to give the kids a chance to think. Hopefully, it's giving the kids a chance to reflect on the choices they've made.' And indeed it is often in OP that a student decides to stop fighting. In this respect, OP works. In fact, the success rate of OP can be understood as a perfect distillation of Tranquility Bay's ideology. If your son is willfully disrespectful, the most loving gift a parent can give him is incarceration in an environment so intolerable that he will do anything to get out - where 'anything' means surrendering his mind to authority.

'I say to the parents,' says Kay, leaning back in his office seat. 'The bottom line is, what's the end result you want? Getting there may be ugly, but at least with us you're going to get there.'