A terrifying figure stalks the classrooms of our minds. He is tall and glowering. In his hand he holds a cane. From his shoulders flutters a black academic gown. He rules by fear and his demands are straightforward: total silence and complete obedience to a set of arbitrary regulations. His name is “Sir”.

He has been around for a long time. He features in Hard Times and Nicholas Nickleby. He walks the corridors of Greyfriars school and glares out of the pages of the Beano. And he still strikes fear into the hearts of grown men and women who left school years ago. I have heard adults confess to trembling with terror at the prospect of meeting their children’s teachers at a parents’ evening.

Why haven’t we left this stereotype behind? Corporal punishment was abolished long ago. Few modern children have ever seen a teacher wearing a gown. Nowadays, pupils are encouraged to work in groups, and total silence in class is a failing not a virtue. The ogre-teacher is an anachronism. Or is he?

Twenty years ago - egged on by my nine-year-old daughter - I wrote a children’s book about an evil, authoritarian headmaster with superhuman, hypnotic powers. As soon as it was published, I began to realise that, quite accidentally, I had stumbled on something potent. Children adored the notion of a demon headmaster. The response to the book was enthusiastic and I soon found myself visiting schools and running workshops. That led to the development of further ogres. For almost 20 years now, I have been inviting groups of children to invent a monster headmistress with some kind of magic ability to control people. The idea never fails to delight them. But why? What makes children enjoy playing with the notion of an all-powerful, evil head? Why do they find it funny?

People joke about situations that put them at a disadvantage. For many children, school seems like that; they see it as a place where they are powerless. Schools are complex institutions and, however much educationists talk about diversity and individual growth, they require pupils to conform. Children must attend when they are told to. They can’t select their teachers or their classmates. They have no say in the curriculum. They must obey the school rules and take the prescribed tests.

Frequently, they aren’t even allowed to choose the clothes they wear. To a generation that sees clothes as a major form of self-expression, school uniform means a loss of individuality - and that symbolises the whole set-up. Like any ogre-teacher, the demon headmaster provides a focus for rebellion because his demand for control is exaggerated.

But unlike other fictional teachers, he is able to dominate his pupils completely. Because he can hypnotise them, they become human robots, unable to disobey. They remember only what he tells them and they speak the words he puts into their minds. Like Mr M’Choakumchild in Hard Times, the headmaster is concerned only with facts, and he chooses which facts his pupils are to learn. He decides what is and is not important. “He has to be a headmaster and not a headteacher,” a reader once explained to me. “Because he masters your head, doesn’t he?” Fear of that kind of control raises the question of what teaching is all about. Is it really a teacher’s job to put knowledge into children’s minds? Does being a good pupil mean accepting everything the teacher says?

Some people think so. I once had a tricky discussion with a woman who attacked me for making teachers’ lives much more difficult by writing The Demon Headmaster. She argued that stories should encourage children to look up to teachers and respect authority. Her implication was that teachers cannot function unless they are seen as perfect and infallible.

Sadly, she is not alone in thinking that. Some teachers feel so insecure that they dare not admit to any ignorance. And some give the impression that they expect mindless obedience from their pupils. “I am sure you would not want your daughter to learn that she can pick and choose which rules to comply with,” a headteacher once wrote to me. I sympathised, but I wish she’d expressed it differently. I don’t want my children to obey unthinkingly. I want them to take responsibility for their actions and to be prepared to stand up for what they believe is right.

That’s why I have always been happy for them to read stories like The Demon Headmaster. They are reassuring, not simply because the ogre-teacher is defeated, but because he is unquestionably the villain. The message is not that all teachers are wicked, but that teachers who aim for total control are bad and ridiculous. In sharing the joke, children and teachers, and headteachers, tacitly agree that education is not about domination. I have noticed, though, that even the most enlightened heads sometimes speak about the demon headmaster with wistful longing. Do they envy his independence? Maybe it’s time I wrote a book about a demon secretary of state for education.

Gillian Cross’s sixth Demon Headmaster novel, Facing the Demon Headmaster, is published by Oxford University Press, pound;4.99. A musical adaptation of the first book, The Demon Headmaster (by Paul James, Iain Halstead, Eric Angus and Cathy Shostak), is published by Samuel French, pound;6.50 for script. Tel 020 7387 9373 or log on to www. samuelfrench-london.co.uk for rights enquiries, to find out about the CD or to read the score