In To Kill a Mockingbird, the events are related by Scout as a child and as an adult. The reader gets the perspective of a child but also the hindsight and wisdom of the adult. As Jem and Scout become more aware of the culture of Maycomb, they learn more about race, racism, and social class differences. In learning about these flaws of the adult world, they gain knowledge and insight but they certainly do lose the innocence (or naivete might be the better word) they once had. In discussing these kinds of issues, Jem comes to a poignant conclusion that Boo Radley might choose to stay inside in order to avoid flaws and hypocrites of the adult world: 

“That’s what I thought, too,” he said at last, “when I was your age. If there’s just one kind of folks, why can’t they get along with each other? If they’re all alike, why do they go out of their way to despise each other? Scout, I think I’m beginning to understand something. I think I’m beginning to understand why Boo Radley’s stayed shut up in the house all this time… it’s because he wants to stay inside.” (Chapter 23) 

Racism is certainly a main theme in the novel. Bob and Mayella Ewell use Tom as a scapegoat, thereby revealing their own racism as well as the racism that exists in town. They know that if Tom is accused, he is likely to be convicted because the jury will be all white and it is likely that they will not be able to see the truth but for the racist perspectives handed to them by their ancestors. Note that Mayella's loneliness results from being forced into the position of mother to all of the Ewell children. She reaches out to Tom for help but also for companionship. When Tom rejects and Bob Ewell beats her, she takes that loneliness out on Tom (although she was probably forced by her father to do so). 

Atticus is the model of courage and ethical behavior in the novel. Jem and Scout learn from his example, in what he says and does. He willingly takes the trial because he knows he is Tom's best chance, difficult though it would be. He has the courage and intelligence to think about everyone's perspective. There are countless examples of this. One example is when he allows Bob Ewell to get away with spitting on him. He explains his thinking to Jem: 

“Jem, see if you can stand in Bob Ewell’s shoes a minute. I destroyed his last shred of credibility at that trial, if he had any to begin with. The man had to have some kind of comeback, his kind always does. So if spitting in my face and threatening me saved Mayella Ewell one extra beating, that’s something I’ll gladly take. He had to take it out on somebody and I’d rather it be me than that houseful of children out there." (Ch. 23) 

A lot can be said in terms of roles and education in this novel. Scout is torn between Aunt Alexandra's expectations of her to be a lady and her (Scout's) own desire to be a tomboy and more importantly to be genuine. In terms of education, it seems pretty clear that Jem and Scout have an advantage over other children and this is because Atticus is such a good father and good teacher. If all the other children in Maycomb had a parent like Atticus, the next generation of Maycomb's citizens would likely be more courageous, educated, and just.