First thing on Monday mornings, which in winter can mean half an hour before sunrise, Lena Davidson’s class relaxes to classical music. Some will sit at a table and read while others lounge on a sofa. One or two might lie on a table, and one can usually be found on the floor beneath it. To Ms Davidson, the details of posture and position are immaterial. The point is that teacher and pupils together have what she calls a “soft landing”, a “safe start” to the week.

She has followed this routine with the same children since they were seven and, in the few years she has taught them, she has learned to read their faces in that first 20 minutes; to know how they are feeling and what sort of weekend they have had.

Not that too many bad things happen here in this comfortable part of Stockholm. Apartments are expensive, and many children at the Tullgaards municipal, or “community”, school for six to 13-year-olds are from middle-class families. But that is no guarantee of safety. Not even in Sweden.

Cross one of the many expanses of water that make the sobriquet “Venice of the North” more appropriate for this city than for many that assume it, and you are at once in the centre. Here, in the same street as the embassies of Turkey, Bulgaria, Cuba and Poland, are the offices of a charity called Barnens RAtt I SamhAllet (Children’s Rights in Society), or BRIS. Founded in 1971 in response to the murder by her parents of a four-year-old girl, it is Europe’s oldest counselling helpline for children, predating its British equivalent, ChildLine, by 15 years.

In a country where even mild physical chastisement of children has been illegal for more than 20 years, it is perhaps surprising that such an organisation receives 75,000 calls a year, and several thousand more emails, detailing the physical and sexual abuse of girls and boys. But as Gunnar Sandelin points out: “Every society has these problems; you cannot eradicate it.” Ten years ago, Mr Sandelin, a former journalist, became one of 400 trained counsellors who sit at the end of a phone for four hours a day, taking calls from children who, despite living in what is arguably the world’s most child-centred society, are victims of sometimes severe cruelty. “After six months, I finished with it,” he says. “It was so hard.”

He then became publicity officer for Bris; his mission, to persuade Swedes that, even in a land where “our children are unbeatable” has become a familiar slogan, there is still no knowing what goes on behind closed doors.

For 10 years, bullying has remained the single biggest cause of distress to children in Sweden, and sexual aggression, particularly among girls, figures increasingly in the charity’s annual report. “We are living in a tougher society,” says Mr Sandelin, “and sexual messages are everywhere.”

At the same time, it seems that Sweden is not immune to the rapid increase in self-harm and attempted suicide among girls that has become an international phenomenon. “We are terrified about that,” he says. “We are getting so many emails from young girls who are cutting or burning themselves, and who don’t want to live. Often they have been sexually abused or had a severely unhappy childhood for various reasons. They have low self-confidence, but can be very verbal when it comes to telling us these things.”

Mr Sandelin has read the notes of every call Bris has received in the past 12 months, and has clearly found the experience distressing. “The most important thing,” he says, “is to give voices to those children who are calling us, and to try to make the public aware that we have children in this country who live in misery you can’t imagine.” Implicit in his words is the message that in Sweden, particularly here in the more prosperous south of the country, this misery is especially shocking.

And stepping out of his office on to the streets of a city that, with a population of just one million, is one of the world’s safest capitals, it’s easy to see why. Here are all the trappings of an enlightened, advanced society that clearly cares about the welfare of its young people; not in the swooning, adoring manner that is such a central part of Mediterranean culture, but in practical, respectful ways. In museums and galleries, parents with young babies have none of the embarrassed furtiveness of their British counterparts. Rather, they don slings and carry their offspring with pride, safe in the knowledge that their buggies are stowed in secure, covered parking ranks outside.

At a science centre, toddlers casually dismantle realistic plastic models of foetuses, while at Junibacken, Stockholm’s intelligent answer to Disneyland, it is said that so many of the city’s top set designers were employed in bringing to life the books of children’s writer Astrid Lindgren that, for the 18 months it took to construct, theatrical life in the capital virtually ground to a halt.

Yet for all the appearances of a youth-topia, there are many who, like Mr Sandelin, are far from complacent. At the office of the Barnombudsmannen, or children’s ombudsman, which was set up in 1993, the struggle for hearts and minds is fought on a daily basis. And nowhere is there greater awareness that the price of enlightenment is eternal vigilance, and that the pendulum that has put Sweden at the forefront of children’s rights can at any time swing back.

“Are we afraid that public opinion is slipping? Of course we are,” says Ulla Tillgren, press officer to the ombudsman. She is thinking about the recent case of a man reported to the authorities for hitting his stepdaughter in a public car park. “The court thought she had provoked him by spitting in his face, and that it wasn’t that bad. But an appeal is on its way.”

It is a case that has split public opinion. But the ombudsman’s office has a statutory duty to campaign on behalf of children, and if that involves repeatedly fighting the same battles, then so be it. “As we say on our website, and as any three-year-old will tell you, nobody is allowed to hit a child,” says Ms Tillgren. “How can you hit someone who is dependent on you? That is the last person you should hit.”

Websites, reports, seminars and surveys are the instruments of persuasion that mother-of-three Lena Nyberg, the current ombudsman, must rely on as she champions the rights and interests of children as set out in the United Nations Convention on the Rights of the Child (UNCRC). With her staff of 25, she writes articles for the national press and canvasses opinions from schoolchildren and students throughout the land, always with the aim of raising awareness, forming opinion and, ultimately, putting pressure on government. “People say to us that the UNCRC is just for children in poor countries,” she says. But she tells them about the plight of Swedish children in custody, and those whose parents are in prison; about the thousands who suffer abuse at home, and the thousands who, year after year, continue to be bullied at school.

“We have a lot of problems in Sweden,” she says, “just like the rest of the world.” And her tone says that she, too, is concerned lest people at home and abroad take her country’s liberal ethos for granted, only to wake up one morning and find it gone.

Not that there is much evidence of backsliding in the fresh, light classrooms at Tullgaards. In a scene straight from an Ikea catalogue, Ms Davidson moves among the pine tables, answering questions and offering encouragement while her pupils get busy with their target books - neat portfolios in which the children compile a complete personal record of work done during their 194 days at school each year. “Once a term,” she says, “I have a conversation with each child and his or her parents, and they will use the book to show where they are, and will give their opinion about their knowledge.”

After the child has spoken, Ms Davidson says her bit before inviting the parents to comment. “But I have a conversation with the child before the parents come, so he or she will know what I will talk about,” she adds. “I want them to feel comfortable, not scared.”

And for all the changes that are disturbing the outside world - high unemployment, creeping racism, growing financial pressure on the welfare state -comfortable and not scared is still the order of the day here.

Children, one or two of them lying on the tables, or relaxed on sofas in the cosy annexe that adjoins each classroom, help each other with their work as if co-operative learning were the most natural thing in the world.

“I’m not the only teacher in the classroom,” says Ms Davidson. “For me, it’s obvious. I tell them we all have our own personalities, but we also have to learn to be a group. And that’s not easy, for a kid or an adult.”

And although she might not say it aloud, you can almost hear her add: “Even in Sweden.”