Fair enough. I love the movie and the book, by the way.
And different teachers teach it in different ways. Suppose there was a discussion after every chapter. Dally's relationship with Cherry is not the main theme of the book, but it is one of the smaller themes. A discussion about this particular scene would not be unreasonable if a teacher thought it was important, or if a student had a question about it, it might generate discussion. Or we could all move on because there are more important things happening. It's all fair, and perfectly appropriate for the teacher to make the decision re: how to handle it.
In the controversy around this Anne Frank book, do we know how much the teacher focused on that particular page about the menstruation and the breasts? Or did a snowflake parent see it and decide to raise hell based on this one page out of context? You and I would probably both agree that if the teacher planned a whole lesson around that page, it was probably not the most appropriate use of class time (although not worthy of a firing or banning).