Ponyboy's assignment is to write a theme about "anything (he) think(s) is important enough to write about...it isn't a reference theme...(it is his) own ideas and...experiences". The length of the assignment is "not less than five pages". In the last lines of the book, Ponyboy reflects upon the deaths of Bob, Johnny, and Dally over the past week and decides "I could tell peopole, beginning with my English teacher". He goes on to describe how he began writing his assignment:
"I finally began like this: When I stepped out into the bright sunlight from the darkness of the movie house, I had only two things on my mind: Paul Newmand and a ride home..." (Chapter 12).
This line happens to be the very first line in Chapter 1 of the book you have just read, The Outsiders. The end of the book refers back to the beginning, and what the author is trying to tell us is that it is Ponyboy who is the fictional writer of the story. For his English assignment, Ponyboy wrote the theme, or story, The Outsiders.