After the gang were convicted and jailed on Monday the judge ordered the release of CCTV footage of their attacks — surely designed to shock anyone who cares about our society as they see, in graphic detail, what can happen when teenagers lead rootless lives. It is clear that O’Mahoney’s problems began in her early childhood, and that if any steps were taken to help her, they failed.

Her story makes a compelling case for early intervention in troubled families, a point that the Prime Minister endorsed this month when he launched his Respect initiative and spoke about teaching social skills to disruptive people. Teenage parents would be offered £30 a week to attend parenting classes, he declared. You could see that his advisers were thinking along the right lines, but there were two weaknesses in Tony Blair’s presentation. The first is that you don’t have to be intimately acquainted with ASBOs and the overburdened criminal justice system to understand that when trying to change the habits of unhappy people, coercion is not always the solution. The second is that the kind of early intervention the Prime Minister described — and which might have given Chelsea O’Mahoney a chance of a less disturbed life — is already being practised in more than 100 British schools, and because it is done with care and subtlety rather than coercion, it has a remarkable success rate.

The scheme, run by a charity, is called School-Home Support. It operates by attaching a specialist worker to a school and giving them the brief to work with families as well as pupils. The principle is simple: if, by supporting parents, you can help them to solve social and emotional difficulties that seem intractable, you will create happier families, and happier children who are less likely to be disruptive in school or the community.

“We were breeding ASBOs,” says Mark Barnett, head teacher of Westfield Community Primary School in Acomb, York. “If I could see them in the nursery and eight years later hadn’t made any difference, then we were just child-minding. I want aspiration, not ASBOs, so now we intervene. If a child’s got a problem there’s usually an underlying reason. We’re talking about children who would be fine if everything was level. But it’s not level. These children have emotional baggage to deal with before they can even think about learning. If you can help them with the emotional side they are more able to learn.”

Westfield was built in the 1950s for children on the emerging Chapelfields estate. Today the area is in the top 13 per cent of deprived places in Britain, and teenage pregnancy is rife. Westfield, the biggest primary school in the north of England, has 700 pupils, including those in its own nursery. Since Carol Ashby became its School-Home Support worker two years ago, Barnett estimates that her intervention has stopped 15 families from being referred to social services. “You can’t measure that but it saves a lot of money,” he says.

One of Carol’s biggest successes is Vicky, a mother of four who was herself pregnant at 16. She has had two partners, both of whom abused her, and she reached the age of 30 certain of only two things: that she loved her children, and that she was worthless.

It was at this point that she met Carol. Every morning Westfield staff greet children and parents at the doors of the school, noting anyone who might be distressed. When a teacher saw Vicky in tears one morning, she suggested that she talk to Carol. “Vicky was being abused by her partner and she didn’t know what she was going to do,” Carol says. “She would come in to my office every day and have a cup of coffee, she might cry or she might be all right. By being given time to decide what she wanted to do, being given options, she came to believe she could get out of the situation she was in if she wanted to.

“Social services got involved and later she decided to get legal support and go to court. I went with her at each stage as an advocate because if people have to sort things out by themselves they might think they can’t. I’ve been a constant person in Vicky’s life and that’s enabled her to work through the issues and meet professional agents who are intimidating to me sometimes, let alone to a parent who doesn’t know how the system works. I don’t always have the answers when parents ask questions, but I can find somebody who does.”

The key to Carol’s approach is that she neither tells people what to do, nor absolves them of responsibility; rather she offers help to enable them to break the cycles of dependency that have damaged their lives. She has spent many hours listening to Vicky over the past 18 months, and continues to do so as Vicky becomes more independent. So not only has she been able to help a family with profound emotional problems, but her support has helped a parent who grew up with low expectations — common in this community — to start to build a life outside the benefit culture. In turn this is providing a positive environment that will benefit her children.

Carol has 20 years’ experience of working with young people and families. But she is also one of those naturally warm people who glows, not unlike a Readybrek ad, with uncomplicated and positive energy, and this is the foundation of her success.

Although she is independent of the school — her salary and the associated costs of employing her are paid jointly by charitable trusts and the school, which contributes about £30,000 a year — she understands that finding the families who need her help depends on her being part of it. Building relationships with parents is not predicated on identifying a problem, but by making herself available she hopes that parents will feel comfortable enough to approach her.

“You can’t just start talking to them cold about going on a parenting course,” she says. “Who am I to tell them, because all they’ll hear is someone telling them that they’re a crap parent. It’s not about that, it’s about growing as a parent, sharing the difficulties and the things that worked for other parents, and you can only start to talk about that when you’ve got some sort of relationship with them, when they know you’ re not there to belittle them, you’re there to enable and empower them, as a parent, as a person, as a family.”