Roger may behave badly because he is not happy at home. He lives with his step-father, who always compares him to his brother; and to his step-father's eye, Roger is not as good as his brother. His mother cannot do anything. Roger tries to behave, but boys will be boys, and one day it just happens: he accidentally throws a hairbrush into the face of his teacher, Mademoiselle Mumu. Mumu and the headmaster both like Roger; but they must set an example and Roger is expelled again. This time, he cannot avoid to go to a reform school. Roger suffers so much that he runs away in the rain and seeks Mumu.
The story seems so real. I read that it is some sort of autobiography by writer/director Joël Séria. It also reminds me of someone. [How many French boys were expelled from several schools in 1947?] Balthazar Dejean de la Bâtie who plays Roger is a beautiful boy, makes it easy to sympathize for him. I feel it's his parents's fault. When he tells the headmaster and Mumu how his parents often don't pick him up for week-ends, I really feel that they don't care for him. The most moving scene is when he tries to commit suicide. It will be a great lost: a boy that smart, that good looking.
Sylvie Testud plays the title role and she is very good as Mumu: a strict teacher who doesn't hesitate to punish those who are not paying attention and don't behave, but in the end, we see that she loves Roger. "I'll keep you," she says to him.