Long-time teacher Barbara Covett (Judi Dench) doesn’t even pretend to care anymore. The other teachers come back from summer break with thoughtful reports — or apparently thoughtful reports — on their departments and their plans, but she turns in three sentences, concluding that the history department’s results are “below the national average but above the level of catastrophe. Recommendation: no change necessary.”

She feels that the world is deteriorating around her. They used to confiscate cigarettes and dirty magazines from the students. “Now it’s knives and crack cocaine,” she says crisply. “And we call it progress.” At school, she no longer tries to teach or worries about holding the line. She just wants to get through it — and then to go home to feel superior about the students and other faculty members when she writes about it in her diary, a pen dipped in acid and special entries embellished with gold stars.

But her name isn’t Covett for nothing. As soon as she sees “artfully disheveled,” sweet-natured, but weak-willed new art teacher Sheba Hart, Barbara wants something very badly indeed. But what?

Her first reaction is contempt, with just a touch of curiosity. She almost despises Sheba for being ineffectual, but is glad for the chance to rescue her by stopping a fight between two students, showing off her ability to command obedience if not respect. When Sheba invites her for lunch, she is girlishly delighted, having her hair done and dressing up. She allows herself to feel special, noticed, wanted.

But she gets to Sheba’s house and it is not special after all. Sheba is married to a benign but shambling older man and is the mother of a surly teenage daughter and a son with Down syndrome. Sheba, a little tipsy and careless by nature, confides in Barbara, who feels special at last. Her secrets are like treasure locked in Barbara’s safe deposit box.

But then Barbara finds out that Sheba has a secret she has not shared. Sheba is having an affair with a 15-year-old student. Barbara finds this both intoxicating and infuriating. She had briefly thought of Sheba as a kindred spirit — or thought she thought of her that way. But now she has something even better — a reason to feel superior, all the pleasure of feeling contempt for someone who is young, beautiful, loved, and has a house in the Dordogne, and, best of all, the power of a secret. She can look around the school and enjoy knowing something no one else knows, and she can enjoy looking at Sheba and knowing she is in her power.

An incisive script by Patrick Marber (Closer), based on the novel by Zoe Heller and brilliantly ruthless performances by Dench, Blanchett, and Bill Nighy as Sheba’s husband make this an intense psychological drama with the urgency of last night’s news.

Parents should know that this movie has very strong language and explicit sexual references and situations, including adultery and an adult teacher having sex with an underage teenager student. A predatory homosexual interest is a factor in the plot. Characters drink and smoke. There are disturbing emotional confrontations, a sad death of a pet, and there is some brief violence. A strength of the movie is the portrayal of a loving and supportive family of a Down syndrome child.

Families who see this movie should talk about what was important to Barbara and Sheba and about how they thought about (or did not think about) the decisions they made. What is the significance of the characters’ names? Of the final scene? Of Sheba’s being a potter and Barbara’s being a history teacher? Who was the predator in Sheba’s relationship with Steven?

Families who appreciate this movie will also appreciate The Prime of Miss Jean Brodie, The History Boys, and All About Eve.