Jive Junction [1943] [DVD]

Classically-trained young musician Peter Crane transfers from the Conservatory to Clinton High School, where he discovers that his music is in conflict to that of the high school's world of jive and Hep Cats. Claire falls for Peter, who is warned to stay away from her by Grant Saunders.

Later, for fear of hurting his hands, Peter backs down from a fight with Saunders and is deemed a coward by Claire and his classmates. That day he gets home to find that his father has been killed in action overseas. He turns to jive and is soon leading the school band, which is entered in a national contest.

On the night of the finals competition, through an accident, the band has no instruments. Peter rushes to his old professor at the Conservatory, who lends him the instruments from a Symphony Orchestra he conducts. ~ imdb