Major themes in Harper Lee's To Kill a Mockingbird are growing up, closely aligned with change. In flashback, Scout (Jean Louise) recalls many changes that occurred over several summers—when Dill came into their lives, and when Atticus defended an innocent black man in a community of the South that still tasted on its tongue the bitterness of defeat in the Civil War. Scout saw her town as a small sleepy place, with little going on to engage her interest.
Maycomb was an old town, but it was a tired old town when I first knew it [...] A day was twenty-four hours long but seemed longer...there was nowhere to go, nothing to buy and no money to buy it with...
This was Scout's view of the world before Dill came to visit his aunt and changed the Finch children's lives forever. While loss of innocence is an important theme, this applies more to Jem than to Scout. Jem is devastated by the outcome of Tom Robinson's trial, but Scout still does not understand the complexities of what occurred when Tom was found guilty.
With growing up came change—in the lessons Scout learned and in what was expected of her. One thing Scout struggled with was behaving in a lady-like manner. When one of the boys in the schoolyard said something nasty about Atticus, Scout was quick to engage in a fight. At Christmas, when her cousin Francis did the same thing, Scout socked him in the face. However, when the news of Tom Robinson's death comes to the Finches' back door, Scout is called upon to be the young lady her Aunt Alexandra had despaired ever to see. As Calpurnia leaves the missionary ladies' tea to take care of Helen Robinson, Miss Maudie and Aunt Alexandra hide their grief over Tom's death and re-enter the room to serve the women coffee and dessert. Scout does the same:
With my best company manners, I asked [Mrs. Merriweather] if she would have some [cookies].
After all, if Aunty could be a lady at a time like this, so could I.
Scout learns that mockingbirds are to be protected because they never harm anyone, but simply bring pleasure with their song; she eventually realizes that Boo Radley is like a mockingbird. In Chapter 30, though it's not clear exactly how much Scout understands, she agrees with Heck Tate's decision to protect Boo.
"Mr. Tate was right."
Atticus...looked at me. "What do you mean?"
"Well, it'd be sort of like shootin' a mockingbird, wouldn't it?"
Scout's understanding of this sophisticated piece of knowledge shows not only how much she has grown up, but illuminates an important change in Scout in how she sees the world—especially Boo Radley. At the start of the story, the kids were curious and believed rumors about Boo. For a long time they spent countless hours trying to learn about him, see him or even get him to come out for ice cream: simply because he was a curiosity. In many ways, the children viewed Boo as many of the adults did: Boo was nothing more than a spectacle—not a human being with feelings or intelligence. By the story's end, Scout understands something about putting herself is someone else's position:
You never really understand a person until you consider things from his point of view...until you climb into his skin and walk around in it.
When Scout finally meets Boo, she sees a broken man with a gentle, protective heart—deserving of respect. Walking him home...
...if Miss Stephanie Crawford was watching from her upstairs window, she would see [Boo] escorting me...as any gentleman would do.