The Naughtiest Girl is a Monitor
Enid Blyton
 It is the story of Elizabeth Allen, who is made a monitor and then risks her position by accusing Julian, a fellow student, of being a thief who tricks her and making her lose her place as a monitor, by playing tricks on her such as making irritating water drops fall on her head, making her books fall thrice, making the teacher to send her out and putting sneezing powder in her book which enters her nose on opening the book and tickles her nostrils, causing her to sneeze. Elizabeth also quarrels with another fellow student, Arabella Buckley, who is vain and selfish and disobeyed the school rules about pocket money. She also makes a midnight feast for her birthday. Elizabeth then sees Julian taking biscuits from the old games locker and thinks he is stealing. She is made to resign her position as a school monitor but ultimately gets it back when she saves a small child from drowning. The real thief- Martin- is discovered at last and admits to having deliberately framed Julian. But unfortunately, in the process he had got Elizabeth into trouble.But at last there was a happy ending.