Claudine at St.Clare's
 When Pat and Isabel arrive at school, they are surprised to meet a new matron. Then French teacher Mam'zelle introduces Claudine, her niece, who will be joining them for this term. Alison O'Sullivan, the twins' rather silly cousin, meets and befriends Angela, who is rich, beautiful and well dressed. Soon, Alison is completely under the spoilt, snobbish Angela's thumb. The new Matron's daughter Eileen is a reserved girl who is later identified as a sneak. Pauline is soon discovered to be a snobbish and conceited girl who continuously brags about her family's 'wealth'. During the inevitable midnight feast the girls find themselves in trouble when Matron is spitefully locked for hours in a broom cupboard by Claudine while they were having the feast. She is furious to find that she is released by her daughter, Eileen, and thinks that she was with the other girls, while actually she was speaking with her brother Eddie, who lost his job but doesn't dare to tell his mother. Eileen is in trouble. Pauline suffers a worse fate than Eileen when her mother visits unexpectedly and is happened upon by Alison and Angela, who mistake the poor, worn-out woman for one of the cooks. Pauline, like Eileen, is exposed as working class. Angela is scornful to discover that all Pauline's boasts of wealth are lies, and that she is ashamed of her lower-class background. The more compassionate Alison, however, takes pity on Pauline's mother, and to her credit, stands up to Angela's snobbish and domineering attitude, vowing to be less in her thrall in future. Alison also makes this action because of the awful behavior of Angela's mother at half-term. Even she felt that though beautiful, Angela's mother was horrible and was also secretly pleased when the brave and mischievous Claudine fell into the water from a balcony so that Angela's mother gets wet even though Claudine hates the water. Near the end of the book Matron reveals that someone is stealing food, money and even stamps from her. It is written that Eileen stole the things in order to feed Eddie and apply for a new job. When Eddie does get employed, Eileen and Eddie go to Miss Theobald to confess about the stealing, for they heard that Pauline had been accused of this even though she had been taking money from her mother's bank account (In a short section also Claudine is suspected for stealing, for she suddenly has a lot of money and buys expensive birthday presents, but it turns out that she sold her lovely cushion cover that Mam'zelle showed to everyone at half term to Alison's mother.) Miss Theobald sends Eileen and Eddie into her other room next door, and calls for Matron. She tells her that she knows who stole from her, and asks Matron whether the girl should be expelled or not, since it was Matron who had been stolen from. The unkind Matron insists that the girl should be expelled, and is then lead to Eileen and Eddie. Matron cannot believe her eyes, and then sees the trap she fell into. She leaves St. Claire's at the end of the year with her children, but Eileen sends a last letter to Alison thanking her for inviting her to eat together at half-term.