Conduct Zero (1986)

Stephen and his friends Linus and William, all in their late teens, loitering out all day with nothing to do. They steal cars' radios for a living. Previously, they are unduly provoked by an instructor at a Cadet School, the three decide to get revenge and steal the car's radio of that Instructor. However, they get caught. Leung, another probation officer, requests to take on their case. Leung is a kind man who loves cycling, he hopes that he could inculcate them an interest in cycling...