Scout is one of the most interesting choices as a narrator that I can think of. Her youth might at first seem like a barrier, but it is because she is young that we can see her as a reliable narrator. She often understands events way beyond her years. The most important lesson she learns is to walk in someone else's shoes, as Atticus teaches her. Because she is learning the lesson for the first time, she is able to scrutinize how it works in the world. She takes in the events of the Tom Robinson trial with an eye of equality, thanks to her father. At the end of the novel, in response to a lesson at school, Scout says, "...Jem, how can you (the people in the town) hate Hitler so bad an' turn around and be ugly about folks right at home-" (Page 249 Chapter 26).
She is allowed to be surprised at the way adults act, because she still believes that people should be consistent in their words and actions. This gives the reader a chance to work through those same thought patterns. She also has the wisdom of an adult narrator looking through a child's eyes. She is surprisingly forgiving of the world's injustices, but still takes it upon herself to act according to her own moral values.
Scout is about six years old when the novel begins. By the end of the novel, she's eight years old.
she is six and by the end she was eight