Ponyboy completely misunderstands his English teacher’s concern. When his teacher tells him he could get a C if he wrote a good theme, he assumes his teacher thinks he has messed up because of the trouble he is in, when in actuality his English teacher understands that life has been difficult for him lately and is trying to help him out.
When Ponyboy’s English teacher keeps him after class, Ponyboy knows he is failing. He says he could do well in English if he tried. The teacher tells him that there is not much they can do about his scores.
You're failing this class right now, but taking into consideration the circumstances, if you come up with a good semester theme, I'll pass you with a C grade." (ch 12, p. 170)
Ponyboy assumes that the teacher means that he was “goofing up because [he'd] been in a lot of trouble” and he is miserable. He does not realize that the teacher knows that the incident with Johnny was difficult for Ponyboy, and he is just trying to help him out. He sees Ponyboy’s potential, and is trying to help him get past the events.
Ponyboy cannot decide what to write about, but then he realizes that people do not understand him or the other Greasers. He decides he wants to help them.
Someone should tell their side of the story, and maybe people would understand then and wouldn't be so quick to judge a boy by the amount of hair oil he wore. (ch 12, p. 93)
Ponyboy decides to write about his experiences, so other people can understand what it is really like to be a Greaser. He sits down and begins writing what eventually becomes the book The Outsiders.