In this book, Nick is a wildly imaginative boy who believes that his teacher is poised against him. However, the ending of the novel reveals that secretly, she was playing a role the whole time. Instead of viewing her actions as authentic indications of her feelings about him or his made up words, now the reader can see that she was conspiring against him to give him the necessary antagonism to make him thrive.
This additional pressure transforms Nick through the plot, making him a hero. This means that Mrs. Granger has played a mysterious role, accepting the role of antagonist, willingly, to help Nick manifest his heroic heights. For instance, the children throughout the book seem to like Nick, and he seems to rise to the top of the pecking order anyway, but when Mrs. Granger and he go to battle against one another over language, word usage, and the classroom, she elevates his reputation.
Nick goes through this journey subtly, not noticing that Granger has helped him. She can be seen as a trickster (the famous archetype), and as a word person. She essentially tricks him into adopting a passion for language. Although he resists her, she skillfully wins without ever really having to try. She puts him in a role to say, "If words are just whatever we say, then I should have the authority to add my words to popular usage." As soon as he does this (to antagonize her, basically), she has won. He is now like her: passionate about language and the invention of words.
