What Social class distinction in to kill a mockingbird?

In TKM there are many different levels of society. Boo is the one that everyone gossips about and doesnt care about. Miss Maudie is the one people look up to Atticus is the one who is judged for defending a negro and negros are looked down apon because of the color of their skin. There is also the man that pretends to be drunk (i cant remember his name) he is ranked as lower because of having a mixed marrige and everyone thinks he is dirt.