By using Scout as the first-person narrator, Harper Lee is able to show how a young girl learns about the pervasive racism in her society. In addition, the author distinguishes between the views of the girl and her older brother. Jem had a slightly wider experience of the inequalities in their town, and his ambition had been to become a lawyer like their father.
After the trial ends with Tom Robinson's conviction, both children are disillusioned but in slightly different ways. They had not seen their father in court before, and they were stunned by his skill and eloquence. One of the shocks they experience, therefore, comes from acknowledging that their father lost. Even worse, however, is realizing that his fine qualities had not mattered in this situation. Most of the jurors had already made up their minds before the trial ever began. Although the deliberations had taken some time, those with doubts had quickly been persuaded to adopt the majority view.
Scout begins to see that the racial divisions in Maycomb are not natural or benign, as she had previously accepted. Her awareness of difference had in some ways been more class-based, as she knew that many townspeople looked down on the Ewells. It shocks her to understand that the all-white jury will side with Mayella just because she is white.
Jem is similarly shocked to confront the fact that racism is so pervasive. His respect for justice, fueled in the courtroom by his father's passionate words about equality, is greatly diminished. The boy is disillusioned by learning that for black people in Maycomb, there is no justice in the courts. His father is powerless to change this harsh reality.