Four young teenage boys run away to the forest one summer night with their heads full of Robin Hood and D’Artagnan; five days later, only three return. The outside world has not been good to them (they are fleeing from the children’s home where they grew up, and where at least one of them has been sexually abused by a housefather), but their retreat under the pines holds terrors, too, and they have brought their personal baggage with them along with their stolen food, money and blankets.

This account of the brutalising existence that the children have endured and the friendship that sustains them makes gripping if not polished reading. It is set three decades ago, but has important lessons for anyone who crosses the paths of contemporary children in public care, or others with emotional difficulties.

Carlton, defender of the weak and emotionally the toughest of the boys thanks to the efforts of a kind carer, is nonetheless at the mercy of his self-destructive, violent temper and is sabotaging his chance of future happiness by refusing to meet his birth mother. Curvis, the expedition leader and the only one at ease in what seems a wilderness to the institutionalised group, is fuelled by rage at being denied contact with his brother. Daydreaming Glenroy, the most vulnerable and mentally unstable of the gang, is pitched into a fresh series of nightmares by hearing the local “Seven Sisters” legend, and his only outlet is his drawing. Bullet’s experience of bullying has driven him to succeed at sports and groom himself for the army.

Their week of freedom, which accounts for just under half of Alex Wheatle’s novel, is a grim parody of the sort of adventures enjoyed by William and the Outlaws. The boys camp out on beds of leaves in a heatwave, scrounge water from a cafe, go skinny-dipping, cut the Scouts’ canoes loose and have a laugh. But their escapade won’t end in a mild ticking-off and a glass of lemonade because they are all in public care and three of them are black (so the white boy on the jacket is misleading).

Wheatle shows through a framing narrative set in the mid-Eighties how the legacy of the boys’ years in care pursues them into adult life with the inevitability of Greek tragedy; their respite in the forest too cruelly brief to undo what has preceded it.

At Pinewood Oaks, they form a cluster of London “problem children”, mostly black, shipped out to the Home Counties, isolated from a suspicious, well-heeled white neighbourhood and parcelled out among the reluctant neighbouring schools, where the one brief classroom scene shows they are despised by the teachers. Their fate rests on whether the “Aunties” and “Uncles” who run their houses within the institution are paedophiles, martinets or humane professionals such as Carlton’s Auntie Josephine.

The worst features of establishments like Pinewood Oaks and their relationship to their communities may now be history, but some of the details of the children’s lives feel as if they will never go away: the lack of privacy, the network of privileges and sanctions underpinning the simplest outing, the glimpses of best clothes laid out for the social worker’s visit. Also timeless is the portrayal of the bond between children who have shared this kind of experience (similar to being evacuated together), reflected in this gang’s “all for one and one for all” philosophy which is sadly not enough to protect them from adults at their worst. The refusal of Carlton, Curvis and Bullett to be victims is moving, especially when we are shown what they have to deal with in later life, and this also transcends the period setting.

The Seven Sisters has been marketed as “Once in a House in Fire meets Lord of the Flies”. It does have the authentic ring of Andrea Ashworth’s novel (the author was partly brought up in children’s homes), but its emotional drive and sound structure are let down by patchy writing. While there are times when Wheatle’s child characters leap off the page, his adults often speak as if they are reading from social services case notes. The more detestable the authority figure, the more painfully clumsy their dialogue. It’s unlikely that the tight-lipped, self-serving housemother Miss Gallagher would have used the expression “too right” in 1976, especially when talking to the police (who are briefly introduced as the boys’ allies; the acknowledgments suggest a link between the novel and a real case).

Alex Wheatle’s earlier novels Brixton Rock and East of Acre Lane are popular with young adult readers but the deluge of foul language in The Seven Sisters means schools would be unlikely to buy it for students. While it might suit some older teenage readers, its viewpoint is that of world-weary adults looking back at childhood in sorrow and anger.