To Kill a Mockingbird does not shy away from social issues of race, class, or gender.
Whenever Scout is scared or disagrees, Jem uses her gender against her.
"See there?" Jem was scowling triumphantly. "Nothin' to it. I swear, Scout, sometimes you act so much like a girl it's mortifyin'." (ch 4)
Gender is a running theme throughout the book. Scout is often ridiculed for being a girl by Jem and told to act like a lady by Aunt Alexandra. Scout is a tomboy. Even her nickname is more boyish than girly.
I could not possibly hope to be a lady if I wore breeches; when I said I could do nothing in a dress, she said I wasn't supposed to be doing things that required pants. (ch 9)
Aunt Alexandra has a very stubborn stereotypical image of what a girl should be. She expects Scout to conform to it.
Another example of the gender differential is in Atticus being a single father. Atticus is not considered the ideal single parent, because he is not a girl. Children are said to need a mother, and he cannot provide a mother’s guidance. He also seems to give some credence to this stereotype by apparently parenting his children as little as possible other than providing moral guidance.
Class is also tackled in the book. The Finches are upper class because they are from an old family. When Scout starts school, she is introduced to Walter Cunningham, who is from a poor proud family, and the Ewells, who are poor but coarse. She learns that there are different degrees of poverty.
The Cunninghams never took anything they can't pay back- no church baskets and no scrip stamps. They never took anything off of anybody, they get along on what they have. They don't have much, but they get along on it. (ch 2)
The Ewells, on the other hand, live like animals. They do not work or go to school. They are vulgar, violent, and stubborn.
"They can go to school any time they want to, when they show the faintest symptom of wanting an education," said Atticus. (ch 3)
The Ewells are the villains of the story, because Mayella is coerced by her violent father into accusing Tom Robinson of rape just because he saw them together.
In Maycomb, segregation and discrimination are in full force. Blacks and whites do not interact except as employee and employer. When Atticus defends Tom Robinson, a black man accused by a white woman, all hell breaks loose. Everyone in town seems to have an opinion.
"Do all lawyers defend n-Negroes, Atticus?"
"Of course they do, Scout."
"Then why did Cecil say you defended niggers? He made it sound like you were runnin' a still." (ch 9)
Atticus, unlike most people, does not feel bothered by defending a black man. He believes people should be judged by the content of their character.
You know the truth, and the truth is this: some Negroes lie, some Negroes are immoral…. But this is a truth that applies to the human race and to no particular race of men. (ch 20)
Lee does not take the easy way out and acquit Tom Robinson. She has Atticus establish that there is no way that Robinson could have committed the crime, and there is no evidence the crime was ever committed. It was a fabrication. Yet because a black man felt sorry for a white woman, he is convicted.