Excerpt from this great article:
When the cheering was done and the MC reported the results... the youngest member (of the losing team) was stunned and almost stomped off the stage in disgust, anger and tears... The audience started to boo—mostly because we had to crush the hopes of some very talented kids in the zero-sum, forced-choice format of the Apollo talent show...
The MC immediately began castigating the audience. "Don't you dare! Don't you dare!" he shouted. "She has to learn, they have to learn, you don't always win. The show goes on and you remain professional. Don't disrespect them or this stage by booing in disappointment. They will have other days. This was not their day."