We lock more children up than any other country in Europe, but what good does it do them?

In the last of a series of special reports, Nick Morrison looks at how life in a secure unit affects young people's attitudes to crime.

"I DON'T like being bad. I'm sick of it. It has got me here. What more can I say?"

Coming from many children, such a bold rejection of misbehaviour would be unusual; coming from Heather, it represents a complete turn-around.

On the out - as life outside is known to the young people inside Aycliffe Secure Unit - Heather had something of a reputation, a reputation she was keen to uphold. She admits it gave her a buzz to think that people were afraid of her.

"From when I was around 12 or 13 everyone knew me as a fighter, someone other people couldn't push around. I'm not proud of it," she says, although it sounds like a boast, before adding: "It was nice in a way, but when people talked to me it was because they were scared of me, not because they were my friend. They would do anything for me; I could get whatever I wanted. When my mum and dad walked around town, people would say 'Look, there's Heather's mum and dad'."

Heather, who's 15 now, has only been in Aycliffe for three weeks, but already it's starting to have an effect. With a six month sentence in front of her, the pressure to be bad is off, and the relief is obvious, although there are downsides. "Here I can be nice, but the worst bit is not being able to act myself. In here, you are not allowed to swear or nothing, and when I'm out, every other sentence is a swear word. Apart from when I'm with my parents."

Life on the out sounds as though it was quite fraught for Heather, despite her hard-woman image. She got involved with a gang, started smoking cannabis regularly, and had regular brushes with police.

Recently, one of her friends was shot dead. She had to miss his funeral, because she had already been sent to Aycliffe.

"Most of us would walk around with at least two guns. We would have a few out-of-towners who would come and try and take you, and it would be difficult to fight them just with fists. I think I would have been dead by the time I was 16 if I hadn't come here. I would probably have got shot.

"I feel safe here. On the streets I'd have a laugh, but I could just walk around the corner and 'bang', and be dead. In here, I know I'm safe," she says.

While it may be tempting to dismiss the idea of armed teenagers roaming the streets as boastful invention, to be thankful for the sanctuary afforded by being locked up suggests there may be something to it. It may be that some youngsters get on the helter skelter, but find when it gets too scary, they can't get off.

Even after three weeks at Aycliffe, Heather says she is determined her life will be different when she gets out, although she's not fooling herself that it will be easy. Once you have fallen in with one crowd, it's very difficult to make a fresh start. Not only do you have to persuade your new friends that you're a different person, you also have to tell your old friends that you don't want to get up to your old tricks again.

"It has made me realise that I can't keep carrying on the way I do. There is no need for it. It really has given me time to think about who my real friends are and where my life is going and where I want it to go.

"When I get out, I will just be a nice person. I will have to be. The ones I know I can talk to, I will just explain to them that it is pointless. My mum always said, 'Why can't you hang around with sensible people?', but they're so boring. I have a laugh with my friends. I know that's a danger," she says.

Centre manager Gill Palin says the two most important factors in preventing children from reoffending when they leave Aycliffe are getting access to education or employment, and forming good long-term relationships, whether it's with family, friends, or partners.

The majority of the young people at Aycliffe have been excluded from school, when their spiralling bad behaviour has become too much for teachers to cope with. A major task over the next 12 months is to set up a through-care team, to help the children settle back into life outside, including finding them a place in school or college.

"If they don't get back into mainstream education, the chances of failure and entering the adult prison sector are much higher, and if we don't rehabilitate and reform them, we will have all these children who go on to serve lengthy prison sentences, and that is a cost to society.

"But our children have been heavily stigmatised through having been somewhere like this, and the services they have been excluded from, including schools, are quite wary of including them again," Mrs Palin says.

The centre's own survey found that 84 per cent of young people released from Aycliffe have stayed out of trouble, but Mrs Palin admits there are a depressing number who return, sometimes again and again. Part of the assessment carried out when they first arrive is to look at whether they have the motivation to change their ways.

"By and large most kids have. I can think of only a very small number who quite like the lifestyle they lead. If you establish that a child is motivated to change, then I would be optimistic that if you get it right outside here, the impetus for change will be there.

"You can usually tell what the outcome is going to be before a child leaves, and a lot of it depends on what support mechanisms they have once they leave. This is the last chance for most kids: if they fail here, or on leaving here, they're highly likely to enter an adult prison, and that way we all lose."

For Heather, Aycliffe has given her enough of an aversion to being locked up that she is determined to stay out of trouble. Whether she'll be able to keep that commitment is another matter.

"I can't wait to get home. I hate being locked up; I like to be out and about, doing stuff," she says. "I have been happier in myself since I've been here. Before, I woke up in the morning and smoked spliff and then I didn't care what happened the rest of the day. In here, I think more of myself. I can't wait to get out and just chill."