I still ask why did Sodapop drop out of school, because in p.13 it says that, "He never hollered at Sodapop - not even when Soda dropped out of school or got tickets for speeding."
I think the theme of the book is about a gang of family members who struggle through life. And I know this because the book 'The Outsiders' is all about a gang that live with each other and that are against another gang.