The School of the title is the College des Musiciens in the Ruritanian kingdom of Mirania, situated in the capital Valnich. It is a special school in the sense that it caters specifically to girls who are highly talented in music.
Jennifer Craddock, an English girl who is highly gifted on the piano is off to join the school as a new pupil. Jennifer's father who was in the navy had died recently as a result of trying to save on of his men who had fallen overboard and Jennifer's only surviving relative is the rather frivolous Aunt Eveleen who wants to send her niece to a fashionable boarding school. But Jennifer is a determined young lady and insists on pursuing her musical bent.
On the train journey to Valnich, Jennifer makes the acquaintance of two girls, Tamara Helston and Daisy Travilla. Tamara is already a pupil at the school and she and Jennifer strike an instant friendship. Daisy is a more empty headed and spoilt girl, who is on a family visit to Mirania, but she proves to have a wonderful singing voice and Tamara suggests that she also join the school. Daisy's mother agrees and she is also accepted as a pupil.
At School, Jennifer quickly finds her feet and makes up a trio with another English girl, Mollie and Tamara who surprisingly turns out to be the daughter of the dead Crown Prince of Mirania, though she or her brother cannot inherit the throne as their other had not been royal.
Daisy takes a longer time to settle down and is at first badly bullied by one of the school's problem pupils, Emily Surtees. Emily has a reputation of bullying and worse of flirting with the young men from the nearby musical Academia.
Meanwhile, as the school concentrates on music, there are exciting events taking place outside in Mirania. A flood and a worker's strike occur simultaneously and the girls are confined to quarters for a while as there is fear of a revolution.