Jonathan is an adopted child who has already run away from eight boarding-schools when he arrives in Leipzig at a school famous for its boy’s choir. He immediately makes friends with four schoolmates who admit him to their secret hideout: an old abandoned railway car. After a run-in with some “day” boys (townies), Jonathan and his friends are punished: they have to stage an “excellent” show for Christmas, by now imminent. They decide to put on “The Flying Classroom”, a “space-age” play whose script they have found. The result should be a terrific rap musical, but precisely the teacher they like best, Justus, vetos this.