She wanted to try and stop him from making up the word, Frindle(pen). He was starting trouble at school from his creativity, recently his word-making. His personality is so much different than his new language arts teacher, Mrs. Granger, and they butt heads. There is a constant power struggle between them. He is very intelligent and rebellious. She is strict and controlling.
On the first day of class he had a "thought grenade" as he refers it. He wanted to know where all the words in the dictionary came from. But she only made him to a report on it.
Nick always has a plan to disrupt class. (He is bored.) The other students like him because his ways of disrupting are funny. He made sounds like a bird in one class.
Mrs. Granger is strict and very serious. She wants total control at all times in the classroom. The two characters really make a funny story when they come together.