One of the reasons, I think, that To Kill A Mockingbird has such lasting appeal to American readers (particularly to American teachers) is that the novel shows a young person developing a fuller respect for humans, even with all of their differences. This development of Scout is set in the Depression era, but the novel is published in 1960, amid the ncreasingly visible struggles for and against racial integration in the United States.
Early in the story, Scout insensitively criticizes the Cunningham boy at the dinner table, for example, for pouring syrup all over his food. She is chastized here, of course, and comes to act in a more mature manner in later instances in the novel, particularly in her views toward Tom Robinson and Boo Radley.
The themes resource given below lists "Prejudice and Tolerance" first in its discussion of several themes in the novel.
In the novel, To Kill a Mockingbird by Harper Lee, Scout changes throughout the story. As a six year old innocent child, Scout is a tom-boy who tries to keep up with her 10 year old brother, Jem. She is willing to fight to keep her place in the games they play, and is willing to fight for what she thinks is right. She doesn't understand at all why her teacher doesn't want her to read or why the teacher doesn't understand the nuances of knowing each family in the town. She learns tolerance from her father when he says, "you never really understand a person until you consider things from his point of view". Scout learns that courage can be watching Mrs. Dubose win her struggle to break her addiction to morphine which helps her understand the courage her father displays in defending Tom Robinson. She grows up a great deal when she must control her temper and her reactions during and after the trial when it is clear that an injustice is being done. Scout, or Jean Louise Finch, changes as she sees her father's bravery in the face of the town's prejudice. She is able to say, "Hey, Boo" to the stranger who saved them when Bob Ewell attacked them, and then quietly walk him home in complete acceptance of the person he is. Her comments as the adult looking back at this time in her life show clearly the effects this time had on the person she becomes.