It has Judi Dench as bitter old Barbara and Cate Blanchett as the hippy-dippy pottery teacher Sheba, who Barbara takes beneath her sinister wing. I pray that they keep a lot of the dialogue intact, for despite the themes of forbidden sex between Sheba and a boy of 15, and repressed lesbian longings on Barbara’s part, it seems to me that every time I pick up this book the real theme is different, and highly relevant to the profession as a whole.

Barbara is not just a lonely, cross old spinster. She is the personification of teacherly disillusion, of the weary malice of the common-room lifer. She despises nearly all her colleagues, especially the optimistically managerialist head, Pabblem. And she thoroughly despises the school, St George’s.

“A holding-pen for Archway’s pubescent proles - the children of the council estates who must fidget and scrap here for a minimum of five years until they can embrace their fates as plumbers or shop assistants.” (That is the one false note in the book. Ms Heller has been in America too long. In real life, Barbara would predict that they’d go straight on to the dole.) Barbara can keep order in class - unlike poor wispy Sheba - simply because she has given up relating to the wild beasts under her care. She no longer cares, or empathises, or particularly wants to help the children. She thinks it a waste of effort, and counsels her new friend against any “worthy, impractical ideas” about building bridges. A wonderful scene occurs when she has been asked to write up the aftermath of a disastrous school trip involving shoplifting and the school being banned from St Albans. Her report on the ringleader reads succinctly: “Gavin is a very nasty little fellow, angry, violent and, I would hazard, a bit mad.” And she calmly asserts, to the head’s dismay, that incidents of unruly and criminal behaviour “would seem to be a fact of school life for the foreseeable future. Given the socio-economic profile of our catchment area, only a fool would think otherwise.”

See what I mean? Is there a Barbara in your staffroom? Are even you - who started so idealistic about the value of every child - being ground down into the weary cynicism she personifies?

Ms Heller’s portrait of the pupils - girls scrapping violently over who put chewing gum in whose hair; dim, leering boys shouting sexual insults at women teachers - makes it clear how easy it would be to reach Barbara’s level of cynicism. If ever there was an argument to give generously paid sabbaticals every five years to teachers in tough schools, this is it.

So let’s hope the film does not cast too many photogenic children in the background, or make use of Dame Judi’s air of wise queenliness. Let’s hope for a cynical old boot and an uncompromising view of just how disillusioning teaching can be. Because the scandal we should note is not only a passing sexual fling: it is the weariness and attrition that can sour the most important profession in the country.