ROALD DAHL has a reputation for subversiveness and political incorrectness, which most people assume is why children love reading him. When his books were promoted in a television advertisement, its slogan was: “Nice children don’t read Dahl”.

In fact, Dahl’s books are a mixture of wild impropriety and very high standards indeed of children’s behaviour — and that of their parents.

Yes, Dahl lets George poison his bad-tempered grandmother in George’s Marvellous Medicine with a concoction that includes paraffin, sheep-dip and engine oil. He lets Matilda put superglue inside her father’s hat. A child in the same novel puts itching powder in her headteacher’s gym knickers. The hero of Danny, the Champion of the World, who is about 10, takes it upon himself to drive his father’s car several miles. And in James and the Giant Peach the horrible aunts Sponge and Spiker are run over until they are “ironed out upon the grass as flat and thin and lifeless as a couple of paper dolls cut out of a picture book”, though the hit-and-run peach is not, to be fair, really under James’s control.

And yet the real point is that Matilda, George and Danny have carte blanche to take revenge on adults because the children are patient to the point of saintliness and the adults are unspeakable. (Which is why the books are funny.) Miss Trunchbull (with the gym knickers) whirls children around her head by their hair and throws them out of the window. Matilda’s father is stupid, greedy, and philistine. James’s aunts beat and starve him. George’s grandmother is unfathomably selfish, and, what’s more, has “a small puckered-up mouth like a dog’s bottom”. And joyriding Danny is rescuing his lovely, poor, poaching father from a trap set by a greedy, braying landowner.

When children behave badly, Dahl has no qualms about their also coming to a sticky end, notably in Charlie and the Chocolate Factory. Gluttonous Augustus Gloop falls into the fudge machine. The television-addicted Mike Teavee is shrunk then overstretched — to end up terribly tall and thin. Spoilt Veruca Salt falls down the rubbish chute, and the gum-chewing Violet Beauregarde turns into a giant blueberry. Willie Wonka, the chocolate-factory owner who effects these punishments, is in fact a dangerous serial torturer of bad children. In the 1971 film version Gene Wilder played him as some sort of almost-madman, but the casting of Johnny Depp, with his sinister pallor, in the new film may be more appropriate.

The books are unrestrained and incorrect but it is clear from them what constitutes villainy. Principally this means the old-fashioned deadly sins: pride, gluttony, greed, avarice, anger and sloth. Plus, in adults, indifference to children, to education and to nature, and, in children, addiction to television, whining and gum-chewing. There are good, sweet, thoughtful children in the books, but there are also model adults who are gentle and attentive to children: Charlie ’s grandfather, Danny’s father, the schoolteacher Miss Honey in Matilda, the sympathetic, storytelling grandmother in The Witches, even the Queen in The BFG.

Bad behaviour in child heroes was never out of fashion, before and after Dahl, from Just William to the Weasley twins in Harry Potter. But are any contemporary children’s writers as unrestrained as Dahl? Certainly many have learnt from him. When Harry Potter blows his awful Aunt Marge up like a balloon, Hermione turns poison-pen journalist Rita Skeeter into a beetle, or vain Gilderoy Lockhart has his memory wiped, the debt is evident.

Child misbehaviour can still be extreme: in Sam Llewellyn’s new books about the Darling children, for instance, they specialise in electrocuting their nannies, while Eoin Colfer’s Artemis Fowl is bad enough to aspire to take over the world. Meanwhile Dahlesque caricatured awfulness in adults is one of the selling points of Lemony Snicket (only Count Olaf fails to get his comeuppance). One contemporary author stands out for combining Dahl ’s morality, magic and humour: Eva Ibbotson. In her Not Just a Witch, for example, it is battery farmers, fur-coat salesmen and white supremacists who are blithely turned into animals or to stone.

One aspect of Dahl, though, is seldom matched. Modern children’s fiction is full of bullies being defeated, punished, made fun of, even tumbled into mud or stagnant ponds. But, apart from the odd moment of, say, Malfoy being transformed into a bouncing ferret, it is hard to think of anyone who is willing to punish awful children with such gleeful and imaginative insouciance as Dahl did.

• The film Charlie and the Chocolate Factory is released on July 29