Scout is a little girl who grows up faster than usual throughout the disturbing events that occurred to her and her family as a result of the trial of Tom Robinson, of which her father was the defense attorney.
Arguably, at age 8, Scout starts to learn about the evils of the world at a fast-paced rate throughout the trial.
First, in chapter 9, Cecil Jacobs tells the rest of the kids at school that "Scout Finch's father defends "n**rs". While Scout fights Cecil about it, she does not entirely grasp the extent to which that statement can hurt her dad's reputation.
Yet, she realizes for the first time that there is a social divide in the otherwise cordial town of Maycomb, and that her father must have somehow crossed a line that should have not been crossed. The thing is, Scout is too young to realize exactly how deep racism is. Remember that she is used to living with a black woman at home; her caregiver Calpurnia. Moreover, "Cal" is a vital member of the Finch household, and she is deeply respected. Scout will continue to taste the ugly flavor of discrimination and will witness first hand the sadness of a town divided.
Another incident also involves defending Atticus in chapter 11, who is now being dubbed a "N-word lover" by the people. Scout, who knows that her father is a man of the law who helps others, is shocked to see that these very people whom her father would gladly defend in court, are insulting him in such a way. Thankfully for Scout, her father is unmoved by the name-calling, and even explains to Scout, step by step, how such insults have often neither objective nor foundation.
Scout also relates the incident of reverse-racism she experiences in chapter 12, when Calpurnia takes her and Jem to church. Since her church is attended exclusively by African Americans, Scout also notes the division in Maycomb extends even to the point of worshipping God. Worse still is the contemptuous reception that Lula, a church goer, gives Cal when she sees the kids:
‘You ain’t got no business bringin‘ white chillun here—they got their church, we got our’n. It is our church, ain’t it, Miss Cal.
Just imagine all of this happening, one event after another, through the eyes of a kid less than 10 years of age. Maycomb must have been to Scout a place that showed its true colors, and the colors were not at all pretty.
Scout was still to learn more. When Robinson's trial is held, she saw the manner in which Bob Ewell behaved in court, disrespected her father, and spoke ill lies about Tom supposedly attacking his daughter.
Most importantly, in chapter 18, Scout witnesses Mayella's testimony and was even more shocked to hear that the woman assumed that Atticus's politeness meant insult.
I wondered if anybody had ever called her “ma’am,” or “Miss Mayella” in her life; probably not, as she took offense to routine courtesy. What on earth was her life like? I soon found out.
And here is the next lesson Scout learns: That not all fathers are as good as Atticus. That there are fathers who abuse their children, and that Mayella has been abused by Bob Ewell.
As Atticus makes the story of Tom Robinson's alleged rape implode in court, it is evident that, if anyone should be on the stand accused of rape and battery, it should be none other than Bob Ewell himself. Scout will nearly suffer the consequences of Ewell's wrath toward the end of the novel, making it yet another eye-opener of how the Finch family's ethics and honesty do not preclude evil people like Ewell from attacking good people such as them.
Of utmost importance is the incident in chapter 15 where Scout convinces Mr. Cunningham to dismiss the lynch mob that he brought TO KILL Tom Robinson at the jail while Atticus was there in vigil. How is that for an eye-opener? The father of one of the kids at school putting all the other dads together to go lynch someone!
The entire novel basically encompasses the series of events that opened Scout's eyes to the world. These, and many other mayor and minor discoveries combined to recreate the events that took place in Maycomb, narrated through the eyes of a now-grown up Scout. It is evident, from the way that her character analyzes it all, that the world around her changed in its entirety, and not necessarily for good.