Why does Atticus insist that Jem read to Mrs. Dubose? What does Atticus want the children to learn from the experience?
Well, he says that he wants them to learn what real courage is, and we can assume that is true. Atticus was a man of his word. However, since it was a difficult experience, and the children had to continue to read and visit despite that, we can assume he was also wanting to teach them to hold to virtue under difficult circumstances. Finally, he might want to teach the effects of addiction (but that's least important here).