Two boys were coaxed down from the maintenance-shed roof, and Sam set off the fire alarms all night long as usual. One member of staff climbed up to sit in the big oak tree in the front garden, holding on to Matthew, who was very angry and refusing to come down. Lee, who’d been spitting and punching Helen, also needed to be held. This counted as a relatively quiet night.

And so far – it’s 9am on a Tuesday – the children have had a nice morning. For “nice” in this context, read: nobody has physically or verbally abused anybody else, nobody has had to be restrained, and no member of staff has been hurt. The previous night, Carly became so enraged when her computer was turned off that she smashed up the entire room, causing so much damage that social services were called.

It’s not yet clear whether she will be coming back, and that is seriously bad news for Carly, because the truth is that if this place can’t cope with her, then it’s unlikely anywhere else can. There isn’t another therapeutic and educational facility quite like it in the country.

We like to think we’re a nation with a profound love of children, by which we mean our own children mainly. These agitated, feral kids with their feckless parents, ugly rages and nonstop swearing don’t even behave like children. It’s much easier to think of them as monstrous or evil than to face the fact that they were babies just like yours and mine who could have thrived. Every single pupil here is a foul-mouthed, abuse-hurling, brick-lobbing yob in the making. And every last one of them is a very small child who holds inside him or herself a place of utter despair.

Their experience of life so far has taught them they are unlovable and unmanageable, and that’s a difficult state of mind to reverse. All any of them wants is a real mum and dad who don’t keep on messing things up for them. But parents who are living on the edge financially, in poor housing, and who have had sporadic and pretty hopeless parenting themselves, are in no position to bring their own child back from the brink.

The Mulberry Bush school in Oxfordshire – the subject of a film by Kim Longinotto to be shown later this month on BBC4 – looks after children who have been multiply excluded from mainstream primary schools. These are not yet the hooded teenagers of Camila Batmanghelidjh’s Kids Company: the youngest is just 6, the oldest 12. All of them are thought to have suffered significant neglect in the first two years of life, which has a ruinous effect on brain development. Fundamentally they are still babies. The building blocks of their personalities are not joined. They are chaotic, unpredictable and unable to function in a group without disrupting. That’s the theory.

It’s the sounds at the Mulberry Bush that stop you in your tracks. The screams of rage and anguish are a constant backdrop. Every single one of these little bodies in bright red school jumpers is dealing daily with devastating loss, and it’s this: if my mum and dad don’t want me, then who in the world am I?

Sam is so upset today he doesn’t know what to do with himself. He is a tiny little boy with a fury boiling up inside him that he can’t contain. He picks up a chair and throws it. “I don’t want to sit there! I don’t want you to touch me!” Then, yanking his hand away from a care assistant who is by now holding his arm: “Keep away from me, you motherf***er!” He is spitting now, giving it his all. I’m not even sure how this began. It could be anything – wrong chair, wrong book.

Shocked? You will be when you hear Sam’s story. His mum had mental health problems, and from toddlerhood he roamed the streets with his sister, Mandy. When he was five and she was seven, they were abducted and sexually abused at gunpoint in a flat minutes from their home. Their mum was regularly involved with abusive men, who in turn abused Sam. Alone in the house with his baby brother one day, Sam, aged barely six, found a cigarette lighter and set light to some paper; he tried to put the flames out with a glass of lemonade, but the blaze quickly became an inferno. Sam managed to escape but his baby brother died in the fire. Afterwards, his mum’s boyfriend held a knife to Sam’s throat and told him it was all his fault and he didn’t deserve to live. All this guilt and loss and he’s still only seven.

Nearly every child here has had experiences similar to Sam’s. Their personalities are fragmented first by neglect, then by abuse. Sam is so badly traumatised that his behaviour veers from withdrawal to aggressive attacks on other children. On his seventh birthday he trashed his own party. His self-esteem is so low, he couldn’t even allow himself to have a nice time.

His bedroom says everything about his internal world. It’s grim and spartan, a terrible place to be. He has ripped the curtains from the window and smashed his furniture. It’s possible that, having stripped it back, he finds the sheer rawness of it comforting. A lot of the children here struggle with having nice things around them; give them toys and books and they’re driven to destroy them.

A freshly painted wall lasts a matter of days before obscenities are scrawled on it. This is the kind of behaviour that takes foster carers to breaking point. When it happens here, there is no drama and everything is made good, but not at once. If this is a child’s only means of expressing gnawing pain, it doesn’t help to paper over the damage and pretend that everything is fine.

On the walls of the classrooms are the usual murals, but these have coloured cards stuck on them bearing messages like “No Violence” or “No Racism”. One of the children has written a story about the Grim Reaper, “who kills people and takes them to hell”: “One minute a person was walking down the lane. The next he was dead on the floor. Something took him away.” There are four residential houses here, taking up to 10 children each – Pegasus, Sunset, Jigsaw and Rainbow – and four class groups named after local rivers. Windrush is the foundation-stage class, where children are assessed when they first arrive. There are five children in Windrush today and they’re working on cards. Pete and Bob, both care workers, and Lynn, the school nurse, are leaving the school. This is always a difficult time: children who are used to being left automatically think: “Was it me? Was it something I did?”

Eight-year-old Lucy, who has a thick, messy plait, is making a card for Pete. She’s applying masses of tinfoil, creating an “arch” for Pete to walk through. “Wouldn’t it be lovely,” she says suddenly, “if you could turn a key and go through a door to a place where everything’s comfy and you could just go to sleep and no one would bother you? Wouldn’t that be lovely?”

Lucy comes up very close when she talks. She’s been so comprehensively abused, physically, sexually and mentally – not just by her own family but by a paedophile ring – that she doesn’t know where I end and she begins. Children with attachment disorders don’t just rage and spit and climb up on roofs: they connect inappropriately to total strangers, looking for warmth. “Can I hold your hand?” she says. “I’m good.”

What is remarkable is that these children bother to invest in new relationships at all. Nearly half are fostered; they have had anything from five to 70 foster placements by the age of seven, and have been excluded from three or four primary schools. The family team try to rekindle relationships with parents. Sometimes the children go home. More often, they have to accept that although they love their families, they’d be better off elsewhere. That’s a hell of a thing to deal with when you’re seven and you just want your mum and dad to love you.

They don’t think: “I’ve been let down.” They don’t have words to describe how they feel; they’re just bundles of raw experiences and they express their feelings like toddlers. The mood in the classroom changes quickly. In Evenlode class one day, Ewan, who has been reading nicely from his book, suddenly freaks when he can’t make out a word. Behind him, under a banner that says “This Is a Positive Thinking Area”, Jonathan, having been asked to sit and read, is losing it. “Jonathan, show me you can calm down,” soothes Karen, a teaching assistant. His book whistles over my head as he pushes her hard: “You f***ing cow.” “Don’t swear at me.” “Then f*** off.”

The staff are hit, spat at, kicked and head-butted on a daily basis. The worst excesses are dealt with by a period of restraint. To be spinning out of control is not only a danger to others: it’s also a very frightening state for a child to be in. For all their stomping and swaggering, these children are desperate for someone to look after them. Holding them on a huge beanbag outside the classroom gives them a chance to take control of their feelings. But most importantly for children who have been serially let down by those who are supposed to care for them, the adults here don’t go away. Staff talk about “an unconditional regard for the child”. Privately they admit they are often pushed to their limits, but they get up the next day and do it all again.

The work of Barbara Dockar-Drysdale, the school’s founder and, with Donald Winnicott, a pioneer of therapeutic childcare, still underpins everything that goes on here. The houses are homely, but they are not home. Coats and shoes are piled up in hallways and there is a pervasive smell of trainers and bleach. The children and their key workers meet as a group every afternoon to talk about how the day went. How do you think you affected others? What was their effect on you? The children’s behaviour often seems utterly senseless and bizarre, and their key workers are constantly trying to understand and create a link: it’s what Caryn Onions, the head of psychotherapy, calls “the struggle for meaning”. Some children regularly pee on their bedroom floors. They smear excrement on their walls. Through a combination of structure, routine and therapy, they’re helped to find an internal sense of “how I feel” and then to express very difficult emotions in a more acceptable way.

The children in Thames class are almost ready to move on; they already spend one afternoon a week at a local mainstream primary. On the wall are written their individual targets. Cameron’s is “Not to threaten others physically”. Tamsin’s is “No A or B incidents” – A and B incidents include actual physical harm to staff and other children, spitting and swearing. As the teacher, Catherine, reads a story, Cameron, who has been busy brushing up glitter from the floor, tips the dustpan over his head. To get the glue he wants, he climbs over two desks. Rory, who is colouring and sorting his Pokemon cards, is listening and provides a running commentary. “Bilbo? Catherine, did you say ‘Dildo’?” Tamsin, who has been sitting quietly, her back stroked by a classroom assistant, throws her feet up on the table. “Oh, for f***’s sake,” she says suddenly. Then, to nobody in particular: “Stop blaming me for everything. I’ve f***ing had enough of it!”

All the children have been helped to find ways of calming themselves down. For Tamsin, it’s writing books. Very reluctantly, she shows me the latest one. It’s all about a little girl who comes home from school and asks her mum if she can go to the circus. It’s full of the kind of warm banter she imagines might go on if she had a safe home to go to. “This is really good,” I say. “It’s not, it’s shit. I ripped the last one up…”

“Well, I wish you wouldn’t, because I think this is really…” But she has already turned away. Tamsin has no time for social niceties. “I want a title for the next one.” She is shouting now.

“Can I help you?” “No.”

Her mum and dad can’t look after her, and at the moment Tamsin hasn’t even got a foster family. She is 10 years old, and deep in her soul she knows that apart from the staff at school, there isn’t anyone in the world who gives a damn about her. During the holidays she is passed from pillar to post, from temporary foster carer to foster carer. At the time of writing, a day before the school breaks up for the holidays, Tamsin still doesn’t know where she is going. At a recent meeting with the 12 professionals involved in her case, Tamsin herself stood up and read from a piece of paper: “You’re not doing your jobs very well. I want to know who’s looking after me.”

Gordon Brown pledged to halve child poverty by 2010 and eradicate it by 2020, but we aren’t even close. Barnardo’s not only estimates that 3.8m children are growing up in Britain without the building blocks of a decent life, but says children as young as nine are being forced into prostitution. The NSPCC has evidence that suggests that one child in six suffers sexual abuse. Most damningly, CRAE, the Children’s Rights Alliance for England, points out that there is still no national strategy to end violence against children.

When these children begin to repeat destructive patterns of behaviour, they are treated with disproportionate harshness by the criminal-justice system. The number of vulnerable children sent to young offenders’ institutions has risen steadily over the past four years, and the latest initiative from Ed Balls’s Department for Children, Schools and Families is a move towards behaviour orders on young children – baby Asbos. The concept is so hopelessly lacking in judgment, you’d laugh if it wasn’t so serious.

Meanwhile, the Mulberry Bush school, which can take 40 children a year, is hardly ever full. It costs £123,000 to send a child here for 38 weeks a year. This is more than it costs to keep a troubled child at a mainstream school with a care assistant – which is called “inclusion”, although the child’s behaviour is so off-the-wall that they are not included in anything. But it is far less expensive than forking out to keep them in and out of prison and mental institutions for the rest of their lives. Sadly, local authorities, who must foot the bill, are not in a position to estimate how many thousands of pounds will be saved by the criminal-justice system in the future; they must balance their own books now.

The Mulberry Bush school serves the whole country. John Diamond, its chief executive, believes it’s a therapeutic model that could be re-created nationwide. There are no miracles. The school can’t take away what’s happened, but it can give a child the tools to help them move on. For the past two years the Mulberry Bush has been classed “outstanding” by Ofsted. The school’s own data are impressive: incidents of aggression by children drop by over 95% during their stay. All leavers are able to access learning, against 8% of new arrivals. And 84% whose behaviour made them unable to be looked after in a family have either returned home or been successfully placed with long-term foster carers.

In the film, Ben, 9, calms down by drawing pictures at a big table covered with a coloured oilcloth. He draws pictures of his mum being bored with him. “Do you feel angry with your mum?” asks Fiona, his teacher. “She doesn’t look after me properly,” he blurts out. Then: “It doesn’t feel nice when the anger is coming. I feel lonely and sad.” One lunchtime, Ben attacks his friend Alex with a knife. He is filled with remorse:

“My mum stabbed my dad.” Afterwards he sobs: “I’m dumb, I hate myself, I hate my life.” Robert, 10, whose dad openly admits he doesn’t like him, repeats words that have obviously been said to him: “F*** you, you’re a little bastard,” he chants, over and over again.

Michael, 12, is seen hitting and spitting and swearing. “I’ve lost it for sure,” he says. Then, with a self-awareness he didn’t have before he came to the Mulberry Bush three years ago: “I’m angry about my dad marrying his girlfriend.”

“And what would you like to say to your dad?” coaxes his teacher, Georgina. Michael is suddenly a very lost small boy: “I love you, Daddy, and I miss you so much.”

“A lot of our children do okay in their lives after they leave here,” says Julie, who is seen at the end of the film struggling with a very angry Ben. “We don’t expect them to be pillars of the Establishment, just to be safe and to know that, once upon a time, there was a place where they were loved and cared for.”

An e-mail sent to the head teacher, Andy Lole, by an ex-pupil, now happily married with two children, juxtaposes the unfathomable cruelty of adults and the extraordinary resilience of some children: “At three and a half I saw my mother beat my sister to death. I was sexually abused by my aunt throughout my childhood and endured the worst physical abuse imaginable. I will never forget the school, the love of one teacher, Lorna, in particular and the profound effect it had on me.

“Our only crime was to be born to parents or situations that were at the very least toxic. Sitting under the big oak tree in front of the school with Lorna and all the others whose names are lost to time, they could never have realised the difference they made.”

Hold Me Tight, Let Me Go will be broadcast on BBC4 on Thursday, May 22, at 9pm

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