The classic radio broadcast Mr. Maxwell plays in his classroom during the science demonstration is the Hindenburg disaster.
Mr. Maxwell is a science teacher. He likes to entertain his kids with fancy demonstrations, including sound effects. The radio broadcast is his big thing. Mark “spoiled the best part of the demonstration” without realizing it, when he said that the balloon was going to explode and that was probably what happened to the Hindenburg. Mr. Maxwell tries to engage Mark, even though he is annoyed, but Mark doesn’t take the bait. He does not discuss what he might know.
Then he punched the Play button on a cassette player and the room was filled with the classic radio broadcast of the Hindenburg disaster, with the announcer wailing, “Oh the humanity, the humanity! as he watched burning people fall to the ground. (ch 6, p. 43)
Mr. Maxwell continues with the demonstration, and although the kids pay attention “pretty well,” the effect is not the same. Mark ruined it. He does not even watch. As the demonstration ends, Mark is looking out the window.
This is an important event in Mark and Mr. Maxwell’s relationship, because the two have a kind of battle of wills. Mark does not really want to engage in school, but it is not because he is a spoiled rich kid. Mark just feels lifeless and alone. He needs Mr. Maxwell to continue to draw him out.