Jean Brodie is a teacher at an all-girls school called Marcia Blaine in Edinburgh, in the 1930s. Maggie Smith plays Brodie, who is known for her tendency to stray from the school's curriculum, to romanticise fascist leaders such as Benito Mussolini and Francisco Franco, and to believe herself to be in the prime of life—in particular, her sexual prime. Brodie devotes her energy and attention to girls she sees as special or mouldable, who are referred to as the “Brodie Set.” The Brodie Set is initially four 12-year-old junior school girls: Sandy, Monica, Jenny, and Mary. The Set often go to art museums and theatre and have picnics on the school lawn, much to the chagrin of the school’s austere headmistress, Miss Mackay Celia Johnson. Miss Mackay dislikes that the girls are cultured to the exclusion of hard knowledge and seem precocious for their age. She has a grudge against Brodie, who has tenure and was hired six years before Mackay became headmistress, and she makes that tension clear whenever she can.
Brodie boasts to her girls that the only way she will stop teaching at Marcia Blaine is if she is assassinated. Brodie catches the eye of Gordon Lowther [Gordon Jackson], the school’s music teacher and choirmaster, with whom she and the girls spend weekends at his luxurious estate in Cramond. [Gordon Jackson]’s Lowther wishes to marry Brodie, but she still has feelings for Teddy Lloyd [Robert Stephens], the school’s art teacher and an ex-lover of Brodie who is now a married man with children.
As the Brodie Set grow older and progress closer to the senior school, they frequent Teddy Lloyd’s studio, where he paints Jenny’s portrait. Sandy [Pamela Franklin] initially rebuffs a lecherous advance from Lloyd. However, when Brodie tries to manoeuvre Jenny and Lloyd into an affair, and Sandy into spying on them, it is Sandy, resentful of Brodie’s constant praise of Jenny’s beauty, who becomes Lloyd’s lover and muse. Sandy ends the affair because of Lloyd’s continuing obsession with Brodie.
Mary, influenced by Brodie, leaves the school to join her brother, whom she believes to be fighting for Franco in the Spanish Civil War. She is killed shortly after crossing the frontier when the train she is on is attacked. This incites Sandy to tell the headmistress of Brodie’s efforts to impose her politics on her students. The disclosure finally leads to Brodie’s termination, her humiliation compounded by Lowther’s engagement to another teacher.
Before Brodie’s departure, Sandy confronts her about her manipulation of Mary, Mary’s senseless death, and the harmful influence she exerted on other girls, adding that Mary’s brother is actually fighting for the Spanish Republicans. Brodie responds with a series of harsh but astute comments about Sandy’s character, particularly her ability to coldly judge and destroy others. Sandy retorts that Brodie professed to be an admirer of conquerors and walks out of the classroom.
Sandy, Monica, and Jenny graduate and leave the school. As Sandy departs, Brodie’s voice is heard proclaiming her oft-repeated motto:
> Little girls, I am in the business of putting old heads on young shoulders, and all my pupils are the crème de la crème. Give me a girl at an impressionable age, and she is mine for life.
