Set in 1948, music professor Clement Mathieu becomes the supervisor at a boarding school that rehabilitates troublesome little boys. What he discovers disconcerts him: the children are repressed and unhappy. Through the power of song, Clement strives to transform the students. Though at first they are unwilling, the classroom is soon animated with lively and enthusiastic voices. But Clement will find himself under fire from the traditionalist attitudes of the teaching staff around him, who believe that enjoyment has no place within their educational institution.