The main conflict in the story is the conflict between Nick and Mrs. Granger. Nick is annoyed that Mrs. Granger gives too much homework, and Mrs. Granger is annoyed that Nick is being disruptive.
Fifth grader Nick realizes that he has reached the point when school has changed. In fifth grade, real letter grades are given and the focus is preparing for middle school. For the first time, Nick has homework. His English teacher, Mrs. Granger, gives a lot of it. When Nick tries to get Mrs. Granger off track by asking her how words are created, she asks him to do a report on the subject.
Nick researches how words are created—they are invented. He comes up with a plan to get back at Mrs. Granger by inventing his own word. He decides to call a pen a “frindle” and see where it goes. Mrs. Granger is annoyed because she thinks his behavior is disruptive. They both feud over the pen/frindle issue.
And Nick didn’t try to sidetrack Mrs. G again. He had slowed her down a little, but had he stopped her? No way. (Ch 5, p. 32)
Mrs. Granger writes Nick a letter. Ten years later, he reads it when she sends it to him along with a dictionary. She apologizes for her reaction to the frindle incident, but explains why she did it.
But somehow I think I have a small part to play in this drama, and I have chosen to be the villain. Every good story needs a bad guy, don’t you think? (ch 15, p. 99)
Mrs. Granger also includes a note explaining that she has all of her students buy this dictionary, and his word is in it! Nick is rich now. Mrs. Granger opens a package from him, a pen, with a note he wrote in fifth grade explaining that she is his favorite teacher.
The main problem in the story Frindle is that Mrs.Granger is against the word Frindle.