A Prefect's Uncle - P. G. Wodehouse

The action of the novel takes place at the fictional "Beckford College", a private school for boys; the title alludes to the arrival at the school of a mischievous young boy called Reginald Farnie, who turns out to be the uncle of the older "Bishop" Gethryn, a prefect, cricketer and popular figure in the school. His arrival, along with that of another youngster, Wilson, who becomes fag to Gethryn, leads to much excitement and scandal in the school, and the disruption of some important cricket matches. - Summary by Wikipedia