I think the most important event of September is the decision that forces Holling Hoodhood to spend his Wednesday afternoons with Mrs. Baker. Holling attends Camillo Junior High, and all of the students are either Catholic or Jewish. Holling is neither, so he has to spend time with Mrs. Baker while all of the other kids go to their religious studies class. If this arrangement never happens, Holling never gets to play baseball with some Yankee players, perform in a Shakespeare play, and do a bunch of other things. It's important to note that Holling's time with Mrs. Baker in September does not go well. She is not happy about the situation, and Holling thinks that she hates him. I would say that another critical part of September's chapter is that it shows readers that Holling's home life is not good. His mother absolutely will not stand up to Mr. Hoodhood. Mr. Hoodhood cares more about himself and his career than anything else, and there is a lot of tension between Heather and just about everybody else in the family. Finally, Holling's encounter with Doug Swieteck's brother on the soccer field is an important event because it sets up a lot of the story's future conflict between these two characters.