In chapter 11, as Jem and Scout are on their way to town, Mrs. Dubose makes a lot of nasty remarks to them about their attire, their behavior, and Atticus's decision to defend Tom Robinson. Her comments are awful and biting, so on the way home, Jem takes out his rage on her bushes, cutting "the tops off every camellia bush Mrs. Dubose owned."
Atticus makes him atone by going over to her house and apologizing, and offering to restore her beloved bushes. But, while Jem is over there, Mrs. Dubose asks him to
"come very afternoon after school and read to her out loud for two hours...for a month."
Jem desparately wants to get out of doing this, but Atticus tells him that he will do it. So, Jem is stuck going to her house and reading for 2 hours every day. The reading idea was a combination idea from Mrs. Dubose and Atticus himself, and Jem fulfills his duties, even if he isn't happy about it.
I hope that helps; good luck!
Because Mrs. Dubose has shouted insults at the children, Jem returns to her house in a rage and cuts all of her prize camellia bushes. This is surprising, as Jem had been the one to ordinarily keep his cool, as opposed to Scout. As a punishment, Atticus forces Jem to face up to his act and to go talk with Mrs. Dubose. She herself decides the consequences: For a month he must visit her and read to her for two hours, six days a week.
Although Jem only realizes later, this arrangement requires inner strength from both Jem and Mrs. Dubose. Jem must fight with his anger through all of the terrible, cruel things that Mrs. Dubose says about his father the Finch family. It is incredibly difficult for him to be polite to her under these circumstances, he aims to emulate Atticus, and so he keeps his anger under control.
Yet it is Mrs. Dubose who faces true punishment. She is forcing herself to fight her addiction to morphine, which requires great willpower and hidden bravery. This time with Mrs. Dubose becomes an important part of Jem and Scout growing up. Although she is antagonizing and cruel, through Atticus the children learn of her considerable strength of character. They also learn by her example the true meaning of bravery.