You may want to utilize several of Atticus's words of wisdom in your thesis about Scout's perception of how people have changed during the course of the novel. Scout seems to take to heart Atticus's words about tolerance--how it is always best to understand a person when you first
"... climb into his skin and walk around in it."
Atticus's final words in the novel are also useful to Scout's future perspective when he responds to her statement about people--both Stoner's Boy and Boo Radley--being "real nice."
"Most people are, Scout, when you finally see them."
Scout's growing maturity helps her to recognize that many of the initial opinions about her neighbors are not true. Through Atticus's suggestions, Scout eventually sees many of the characters in a different light: Boo changes from the neighborhood ghoul to a watchful and caring friend; Tom's blackness does not make him guilty of the accusations against him; and Dolphus Raymond's actions are not what they seem.
If I was writing a thesis statement for that topic, I would begin with stating how at the beginning of the novel Scout was naive and often spoke out when she should not have. With the help of Calpurnia, Jem, Atticus, and Aunt Alexandra, she begins to realize how people around her town behave and why they do things. Scout learns that the town's gossip is often just superstition, "three quarters black folks and one quarter Stephanie Crawford", and misjudgment of others. When she finally meets Boo Radley at the end of the book, Scout finds that he is just a nice man with a bad family history. She learns to judge for herself the character of a person.