We interview Ed Balls the day after yet another terrible murder of a teenager in London. Sixteen-year-old Ben Kinsella was stabbed four times in the neck and chest following a party to celebrate the end of his exams. Kinsella was described as a model student who was likely to get a string of A grades at just the sort of inner-city comprehensive the Secretary of State for Children, Schools and Families is trying to encourage to succeed against the odds.

We ask him if it is any wonder that parents in modern Britain are worried about their children, with stories like that appearing on the front pages of the newspapers so regularly (17 teenagers were killed with guns or knives in London in the first six months of 2008). Parents such as Cherie Blair, for example, who says she fears for her children on the streets because of gun and knife crime.

Balls is adamant that schools themselves remain a safe haven for children. "There is no evidence in the last ten years of any rise in any of these crimes in schools," he says. "In fact, it almost never happens."

He does recognise, however, that schools have a crucial part to play. "The most important thing to do is to make sure schools are a place where, in partnership with the police, teachers are doing prevention and the kids know that if there's something going on which they are worried about, then they can speak up. It's about a cultural change."

It is exactly a year since Ed Balls took over at the newly created Department for Children, Schools and Families (DCSF) with the express intention of changing the culture of childhood. He is responsible not just for primary and secondary education, but also for strategies on youth crime prevention, youth offending, play schemes, youth alcohol and drugs. Jointly with the Justice Secretary, Jack Straw, he is also responsible for youth justice and, with the Health Secretary, Alan Johnson, for children's physical and mental health. The Children's Plan, a ten-year strategy published in December 2007, is a vastly ambitious attempt to shift the emphasis in policy to the needs of young people.

Under Balls, there has been a marked departure from the more punitive instincts of Blair-era policy and towards children, inside and outside the classroom. The so-called Respect agenda has been quietly shelved and the obsession with Asbo rhetoric curbed. In the classroom, there has been a serious attempt to address concerns about the testing regime. Balls is already looking at reforming tests for 11-year-olds to allow them to be taken when teachers feel the pupil is best prepared. This "testing when ready" approach is designed to be more like a music exam, one which the children enter only when their teacher believes that they have reached a certain standard.

We suggest that above and beyond all the other pressures faced by young children in 21st-century Britain, they are also being tested to within an inch of their lives. Many teachers and parents are in despair at the stress tests - especially National Curriculum tests (SATs) for seven-year-olds - are causing. Balls is initially dismissive of the suggestion that large numbers of seven-year-olds are being traumatised by testing because their parents are warned in advance.

"It doesn't happen in every school," he says.

We agree, but suggest it's quite normal. "It's totally the wrong way of doing things," he says.

The wrong way of testing

But it happens a lot, we say. We know schools that do it. Some of them are quite close to where Balls himself lives in north-east London.

"No seven-year-old should ever know they are doing SATs," he says bluntly. This is an odd answer. We know that he knows that we know what's going on. Schools think they are doing the right thing. We say that many schools send out notes to parents warning them that the tests are coming up and asking them to give their children extra support. It has been suggested that some schools lay on special treats, such as film shows and even sweets, to soften the blow.

The discussion becomes decidedly heated and at one point Balls just shakes his head and says "rubbish". But he also begins to shift his ground: "The best headteachers will ensure that no six- or seven-year-old knows they are doing SATs. I promise you that is the case. If you are telling pupils in Year 2 that they are doing SATs next week then that's the wrong thing to do. You should not be stressing the children."

It appeared to be an issue close to his heart. "They don't need to do the SATs in a sit-down environment," he says. "It's something that can be done as part of the school day. Honestly. And there are loads of schools doing that."

And those that aren't?

"I feel as angry as you about that. I cannot believe they are doing that. They should not be doing that."

Balls has been charged with being too interventionist, too prepared to meddle. On this issue, however, there is little he feels he can do to control the way individual schools run their tests, short of abolishing them altogether, which he is not prepared to do because they are a useful tool for teachers. His frustration is evident. There is a distinct feeling that he would happily wring the neck of every headteacher who announced tests for seven-year-olds in advance this summer, if that wouldn't set an even worse example to Britain's children.

Beyond the stress of curriculum tests, Balls emphasises that most British children's experience of childhood is essentially a happy one. "If you get most of your observation from reading the press, you get really pessimistic about what happens to children and young people," he says. But he also recognises this is not the case for all young people: "There are schools, families, areas, where children are really getting a raw deal. We all get angry about the fact that if you live in a deprived community in terms of income, you are much more likely to be scalded in the bath or be run over by a car in your area, as well as much more likely to not do well at school."

Balls turns to his own experience of childhood in Nottingham to illustrate the point that things were not necessarily better in the past. "When I was growing up, when I was ten, 11, 12, my mum and dad didn't want me to get the bus to watch Nottingham Forest play at home because when you went to the football you got beaten up. In the good old days it was pretty bad, actually."

Yet he does recognise a crucial difference: that the gap between those who do well and those who have a tough time is wider than it was, especially in a context of drug and alcohol misuse. Naturally, he traces this back to the "bad old days" before new Labour. "One of the consequences of the Eighties and Nineties is that a lot of young people had a tough time themselves, and their kids have gone on to have a difficult time as well," he says.

For Balls, the key to tackling youth violence is intervention at an early age, but he knows many schools do not have a good working relationship with the police/social services. It should be possible, he argues, to identify children at risk of problem behaviour by identifying those who have an older brother, sister or a parent who has spent time in custody. But many heads wouldn't have this information to hand.

As the New Statesman hits the news-stands, the DCSF will be publishing plans for legislation to set up "children's trusts" that bring together the various agencies responsible for children in a given area. The move comes as a result of recommendations by Lord Laming following the death of Victoria Climbié in 2000. Laming found that the abuse eight-year-old Climbié suffered had come to the attention of social workers, hospital staff, police and the local authority, but there had been no mechanism to act together to help.

Get to them earlier

Balls points to a number of schools that now have child psychologists, children's health services and advice for parents all located on-site. But he concedes there are still big problems of communication between the various agencies responsible for children. He tells the story of a boy at a school he recently visited, whose father had committed suicide in prison the previous year, and who was playing truant.

The headteacher explained the problem to social services, who said it was too serious for them to deal with. She then went to the agency that helps adolescents with mental health problems, which said the child would have to spend six months on the waiting list. When the head said the problem was urgent, she was asked if the boy had harmed himself, because a physical manifestation of the problem was needed before intervention would be possible. Balls's conclusion is that heads must be given the means to intervene early, and immediate help from other agencies when they demand it.

Despite everything, the Children's Secretary remains positive about the generation now going through the school system. "The majority of kids are doing better in school, have a more stable education, do more volunteering. More are doing music. Actually, they are the best generation of young people we've ever had, and we demonise them stupidly."

As we leave, we ask for a final verdict on the state of the nation's children. "The vast majority are doing great and the ones who aren't, we should be getting them earlier," he says. "And we should help parents to see that the world isn't such a scary place."