Mademoiselle Nitouche(1954)

Celestin works as an organist at a girl's school. By day, Celestin is the meek and mild target of the girls' incessant practical jokes. By night, however, he is the celebrated composer of popular operas -- and the romantic vis-à-vis of a celebrated stage star. When schoolgirl Denise stumbles onto Celestin's secret, she threatens to tell all -- but only if Celestin refuses to escort her to the opening night of his latest opera. As a result, Denise falls in love with a handsome young soldier, while Celestin is accidentally shipped off to an army camp. A series of silly coincidences brings happiness to all concerned by fade-out time.