Prejudice is certainly one of the major themes to be found in Harper Lee's novel, To Kill a Mockingbird, but it is not restricted to only racial bias. Discrimination of many types pop up in the story, and young Scout is a witness to much of it.
RACIAL. Racial bias is the overriding theme for most of the play, with one of the two main plots culminating in the unjust charge, conviction and, finally, killing of Tom Robinson. Blacks are often referred to as "niggers," though Atticus warns his children that it is not proper. Maycomb's blacks are uniformly considered second-class citizens and are segregated at every turn. They are blamed for nearly every unexplained event in the town, from the disturbance in the Radley yard to the rape of Mayella Ewell.
CLASS. Discrimination of the various social classes is rampant throughout the novel, from the treatment given poor, young Walter Cunningham by the schoolteacher, Miss Caroline, to the hatred directed to Maycomb's lowliest family, the Ewells. The Cunninghams and their widespread kin live in Old Sarum, well outside of town; the blacks live on the outskirts of town; outcasts, such as the Ewells and Dolphus Raymond, live apart as well.
GENDER. Females are still treated with kid gloves by the heavy-handed male populace. Women are not allowed to serve on Alabama juries in 1935, and most of the single females of the town--such as Miss Maudie and Miss Stephanie--are regarded as suspicious crackpots. Scout is relentlessly reminded that she is unladylike. Women are portrayed primarily as gossips and housekeepers. Have you noticed that not a single woman in Maycomb is employed?
AGE. Children's rights have still not made much headway in 1930s Alabama, though Jem and Scout are certainly given more independence from their liberal-minded father than most children of Maycomb. Poor children, such as Walter Cunningham and Burris Ewell, are treated in a much different manner than others; Dill and Francis are shuttled off to their relatives for long periods of time; meanwhile, there is no mention whatsoever of black children going to school. Even the unseasonable snow is blamed on children by superstitious adults.
MENTAL STABILITY. Boo Radley is considered an outcast by the entire community (as well as his own family) after it is determined that he has become mentally unstable. He is locked in the courthouse basement before being imprisoned in his own home, yet he becomes the single most heroic character in the novel by the end. Dolphus Raymond is thought to be both drunken and mentally abnormal when he takes a black girlfriend and forsakes the white side of town to live across the tracks. He reveals his true character to Dill and Scout at the trial but prefers to keep his secret intact in regard to the rest of the town.