The theme is autumn; paints are russet and green. Model-making involves Mr Potato head-type features on vegetables; cutting and sticking creates mobiles of fruit and vegetables; and the game means pairs of children negotiating an obstacle course and picking up plastic veg.

So far, so normal - except that there is one teacher for every four children, care officers observe every activity, and senior staff act as “bouncers”. Everyone, staff included, wears the school sweatshirt. Everyone also wears a plastic bumbag.

Anthony downs his brush and flees out of the door. The “bouncer” catches and gently restrains him. Reluctantly, he returns. Meanwhile, Jim starts waving his hands and shrieking obscenities. “Shall we paint a leaf here?” asks Sam, one of the teachers. Her voice is full of good humour. Jim paints a leaf. concentration descends over the room. A woman hurries in. “Time’s up.” The children take off their painting shirts.

“Tokens!” says Sam, as she hands out yellow discs. The children carefully place these in their bumbags before leaving.

Thursday co-operative play at Wells Park is theory in action. These are children who weeks before were putting books in toasters or arriving for their week’s schooling half-naked in a taxi, howling.

Now they proudly describe the change. Freddy, who could provoke almost anyone to hit him, says his best friend is “very good at modelling”. Laura,who used to scream for hours on end but can read, helps Peter, who never used to speak and can’t read, to sound out the words of a poem.

Once they were some of the most dysfunctional junior pupils in Essex and London. Wells Park is a residential school for emotionally and behaviourally disturbed children and one of the foremost training centres for their teachers.

Admissions are open throughout the year for up to 40 children. At the time of my visit, there were 38, all but one of them boys. As a group, its eight teachers are more highly qualified than any other special school in the UK (all have degrees at masters’ level or above). Its Office for Standards in Education report was “stunning”, says principal David Wood. It is a place which offers to the most chaotic and confused children a coherent, benign way to restructure their lives.

Its system of behaviour management is based on positive reinforcement and has been steadily refined since it was introduced in 1990. It works because of the consistency and care with which the 30 staff - eight of them teachers - approach their pupils.

Every five weeks, pupils, families and teachers agree targets of improvement and strategies to achieve them. Every five weeks, progress is reviewed. Staff likewise set themselves targets.

Children’s targets might be “to use smaller handwriting”, or “to keep still when I am talking to other people” or “remember I can be heard using my quiet voice”. Staff plans are “to remind him to use his smaller handwriting between the lines and to praise the results” or “to remind her not to fidget when she is talking and to focus her attention back on what she is doing”.

Above all, from the children’s point of view, there are the rewards. Every 15 minutes from Monday morning to Friday afternoon, each child has the chance to receive a token. Every day at 3.45pm after school, the children can cash in their tokens in groups of five known as “giants”. In return they get treats such as the loan of a tape player, books or toys, an evening activity or extra play. More ambitious spenders can save “giants” for outings or shopping trips. It is, says David Wood, “positive, when much of their life has been negative; structured, when they have had lots of chaos; and relational when they have found it hard to be with others. We are also modelling appropriate adult behaviour.”

The tokens allow the teachers to praise and encourage the children. “It is standard,” adds Mr Wood, “for children to increase their reading age by two or three years in the first year they are here.”

Reading is on the timetable, along with meals, lessons, play and bedtime story. If children are to return to the mainstream (and five did last year,while many others could manage special day schools) they need to learn the normal behaviour that was forgotten while they were starting fires, slashing tyres, shoplifting and running away.

Although at weekends some children will return to an unhelpful background, Sonia Burnard, head of training at Wells Park, is sanguine. “We can’t replace the parents. The children have to learn behaviour management at home too. We can’t make their previous lives different, but we can develop new things for them.”

Mrs Burnard is drawing up Wells Park’s application to the Department for Education and Employment to be the first school in the country offering initial teacher training in behaviour management. She rocks with laughter when she considers some of the behaviour programmes which have been used with children such as Anthony and Jim in other schools. “Teachers put a chart on the wall and give the children a gold star now and then. After 10 days they say it doesn’t work. Nothing will work like that - it’s an idiocy. But we have children who couldn’t read, who are said to be considered hyperactive, unteachable really, and we get them sitting down, reading and enjoying life.

“Behaviour management may sound cold,” she says, but it’s not. “It’s warm and it’s cosy, it’s full of love. The tokens aren’t really for the children at all. That’s the secret. The tokens are for the staff, to remind them to praise the children. That’s why it works.”

* all children’s names have been changed.

Wells Park school and training centre, School Lane, Lambourne Road, Chigwell, Essex IG7 6NN. Tel: 0181 502 6442