A group of high school girls are stuck in a remedial maths class for the summer. Through sheer boredom they decide to form a brass band as a way out of the uninspiring lessons. The girls however are more interested in having fun than in actually practising. It is only when their band is threatened with disbandment that they realise they actually enjoy learning how to play even though they aren't very good. The girls turn to their eccentric maths teacher for help as they embark on a wild adventure of musical fun, to the addictive beat of that big brass swing.