At the opening of Harper Lee's novel To Kill a Mockingbird, Scout and Jem Finch are quite young, with Scout being a precocious five and Jem nine years old. There are really two plots to the novel, the first concerning the children Scout and Jem and the second concerning Atticus Finch and his attempt to get justice for Robinson, a black man falsely accused of rape. These two plots work together, in that we see the effect of a strongly moral parent on the ethical development of the children.
We first encounter Scout and Jem indulging in childish curiosity about their reclusive neighbor Boo Radley. They give no real thought to how he might feel at being treated as a spectacle, but are not shown as bad-hearted children, just as young and naive. Their first sign of maturity is their (failed) attempt to place a thank-you note in the tree, a sign that they are polite and considerate children. As the book progresses, the children become aware of Boo's secret acts of kindness and reveal them to their father, showing increased maturity in the way they begin to understand Boo as a real person rather than as just entertainment. Their support of their father's attempt to find justice for Robinson is also evidence of their growing maturity and ability to resist peer pressure.
Jem's relationship with Mrs. Dubose also shows how his father's guidance leads Jem not to react impulsively but to think through other people's histories and motivations before reacting to their behavior. It is also an episode about overcoming fear and understanding that anger is often born from fear.
Another major episode showing the children's increasing strength and maturity is when Scout talks to Walter Cunningham, reminding him that she is his son's schoolmate and defusing the potential for the assembly of people to turn into a lynch mob.
The final resolution of the novel, in which Boo and the children become friends, shows that they have learned to take their place within society, using reason and empathy to relate to people in an adult fashion.