It sure seems to me that a scene was cut from the "school dance." When Lisa dances with another guy, Joe looks on. The guy gets fresh with Lisa and grabs her tie. She pulls away from the guy and he lets go of her tie and she walks away. Then, in the next scene, Joe and Lisa are sitting together at the dance. This is where I think a scene was cut. Something tells me that Joe came to Lisa's aid and consoled her. He probably even straightened her tie and fixed her collar as the guy who grabbed her tie pulled it loose and crooked. When we see Joe and Lisa talking (and Joe is explaining about why he was sent to the camp for juvenile delinquents), Lisa's tie is tied on straight and her collar is fixed.