They are all-seeing, all-knowing dispensers of wisdom. Or they are evil demagogues, sadistically ruling over their pupil-filled domains. This is the school headteacher, as portrayed in children's literature.
Pat Thomson of Nottingham University analysed the characteristics of headteachers in 19 children's novels published over the past 35 years. Her findings suggest that "sadistic" and "evil" characters can help children learn about authority, she told the annual British Educational Research Association conference, held at Warwick University this week.
In the jolly-hockey-sticks era of the 19th and early 20th centuries, literary headteachers would often be portrayed as distant and remote: a God-like figure demanding obedience.
Times and timetables may have changed, but the fictional head remains remarkably consistent. In seven of the novels that Professor Thomson studied, the head was a remote authority figure, dispensing judgment from on high.
"It is the headteacher who is the ultimate authority, with the power to sanction and reward, to discipline and punish," she said.
There are, however, contemporary twists on the omnipotent head. In Andy Mulligan's Ribblestrop, the headteacher favours real-life lessons over textbooks. And Professor Dumbledore must battle against the Ministry of Magic's didactic methods.
But such pedagogical omnipotence can be misused. Gillian Cross's The Demon Headmaster hypnotises and brainwashes his pupils. And, in Peter Wynne-Willson's The Inflatable School, the head develops a corrupt plan to turn his school into an academy.
In fact, power and wrongdoing often coexist: in the 19 books that Professor Thomson examined, nine heads are described as "evil", "sadistic", "messianic", "authoritarian" or "child-hating".
Professor Thomson suggested that real-life headteachers could use children's books to address the uses and misuses of power in school. "The ... reader ... recognises that power can be used wisely and to ethical ends - or not," she said.