Atticus tells his children, "It's a sin to kill a mockingbird". Discuss how Scout shows she now understands what he means by this.
At the end of the novel, Scout shows that she understands what Atticus had explained to her about how it's a "sin to kill a mockingbird." Mockingbirds don't do anything but sing. They don't nest in corncribs and they don't do any harm. That's why it's a sin according to Atticus (and Miss Maudie as well).
In chapter 30 Scout says, "Mr. Tate was right...it'd be sort of like shootin' a mockingbird, wouldn't it?"
Mr. Tate didn't want the news of Boo's rescue to come out. He wanted to let everyone in Maycomb believe that Bob fell on his knife so that Boo wouldn't be swept away by the praise of the town. That kind of recognition would about kill him. Scout understands what he's saying to Atticus and shows him her understanding using his motto in this scene.
Atticus helps Scout understand the meaning behind the mockingbird: a harmless bird with a beautiful voice. Scout is later able to apply this to Tom Robinson, who has done no wrong, but is wrongly sentenced to death and Boo Radley, who is ostracized by the community for no valid reason. Scout sees the injustice with both of these men and is able to connect that to the injustice of killing a mockingbird.
Mockingbirds are simple creatures who do nothing but sing. Scout understands how others can be mockingbirds because Boo Radley was actually the one who saved her and a very nice man in general, yet as she grew up she had thoughts of him being a myth. As she matures she understands how society can create false perceptions of someone and how this can innocently affect them.