In Chapter 11 of "To Kill a Mockingbird," Jem learns Atticus's lesson about not prejudging people. In anger and "umbrage at Mrs. Dubose's assessment of the family's mental hygiene," Jem destroys her beautiful camellias. Then, he pays the consequences of his actions as Atticus makes him read to the ailing woman. It is only after Mrs. Dubose dies that Jem learns that she has courageously withdrawn herself from the pain-killing morphine to which she has become addicted.
While he goes to read to her, Jem learns as Atticus has taught him,
[people] are entitled to full respect for their opinions....[but] she's old and ill. You can't hold her responsible for what she says and does.
As Jem reads he tries to skip words that he cannot pronounce, but Mrs. Dubose catches him and makes him spell it out. From reading to Mrs. Dubose, Jem learns patience, courage, and tolerance of the idiosyncrasies of others. That he has learned this lesson is evidenced in Chapter 13 when he urges Scout not to "antagonize" Aunt Alexandria because Atticus "has got a lot on his mind now, without us worrying him."
When the mob threatens Atticus at the jail in Chapter 15, Jem refuses to leave when told to do so by his father; he courageously insists upon staying in order to try to prevent the men from doing anything to Atticus. Following his example, Scout speaks to Mr. Cunningham so as to defuse the tension of the angry men. By singling him out, Scout makes Mr. Cunningham uncomfortable and the men leave on his direction. Later, when the "full meaning of the night's events hit" Scout, her brother Jem tolerantly
was awfully nice about it: for once he didn't remind me that people nearly nine years old didn't do things like that.
In Chapter 17 the adults think that Scout should not hear what is being said at the trial of Tom Robinson, but Jem tells the Reverend Sykes that Scout "doesn't understand it...she ain't nine yet." Then, when the Reverend becomes anxious about Atticus knowing that the children are there, Jem allays his fears by saying, "He can't see us this far away. It's all right, Reverend."
By the end of Chapter 23, Jem declares that he understands why Boo Radley does not leave his house: the world is too confusing and too corrupt.
If there's just one kind of folks, why can't they get along with each other? If they're all alike, why do they go out of their way to despise each other? Scout, I think I'm beginning to understand something, I think I'm beginning to understand why Boo Radley's stayed shut up in the house all this time...it's because he wants to stay inside.
Clearly, from his experiences with Mrs. Dubose, Jem has learned to see and listen first and form judgments later; he has also acquired courage.