Why is Scout unaware of racism and discrimination in Harper Lee's To Kill a Mockingbird?

In Harper Lee's To Kill a Mockingbird, Scout lives in a very unusual household for her time period in Southern society in that her household is very racially integrated and her father does not express racist views. As a result, Scout does not learn anything about racism or discrimination until she reaches school age.

Scout's household is racially integrated because, even though Calpurnia is the Finches' cook, just like many white Southern households had African-American household servants in this time period, Calpurnia actually has the role of a surrogate mother and is treated like one of the family. Scout's mother passed away when Scout was only two, and Calpurnia began working for the Finches after Jem's birth. As a result, Scout has no memories of her mother, and Calpurnia is the only female role model in Scout's life. Since Calpurnia is often left alone with the Finch children while Atticus is at work, she has very easily taken on the role of surrogate mother, looking after the children, making sure they come home when they need to, and asking Scout "why [she] couldn't behave as well as Jem" (Ch. 1).

Later, Atticus expresses to his sister just how much he views Calpurnia as a member of the household. Aunt Alexandra comes to stay with the Finches just as Maycomb's citizens are feeling heated over Atticus's decision to defend Tom Robinson. Since racial tensions are stirring and since Aunt Alexandra is racist herself, she tries to persuade Atticus to let Calpurnia go. But, Atticus reflects his much more open-minded, unbiased view towards race, contrary to the rest of Maycomb's society, when gives Aunt Alexandra the following very adamant response:

Alexandra, Calpurnia's not leaving this house until she wants to. You may think otherwise, but I couldn't have got along without her all these years. She's a faithful member of this family and you'll simply have to accept things the way they are. (Ch. 14)

Hence, as we can see, as a result of living in a racially integrated family and having a father who is not racist, Scout lives the early years of her childhood not knowing anything about racist views. It is not until Chapter 9 when her peers begin insulting her for her father's decision to defend Tom Robinson that Scout learns anything about racist views.