Some have claimed that Chapter 16 is the most important chapter in the entire book. What happens that makes this chapter so important?

Chapter 16, "Field Day," delivers the body blow the author had promised. Only the younger children manage to have fun anymore at this event, and Zinkoff's terrible performance, despite his best efforts, earns him the name that is the novel's title. Zinkoff is no longer unaware of the cruelties of the other children, and he is so hurt that he bursts into tears the moment Polly mentions winning. The time that was foreshadowed previously has now arrived when a kind and happy child is faced with cruelty. He must now look within himself to find the strength to overcome the meanness of others. Rejection and believing in oneself are major themes in the book.