In the novel To Kill a Mockingbird, why does Scout become more aware of prevalent racism throughout her community?

Tom Robinson's trial for rape makes the previously latent racism in Maycomb clear to Scout. Before this time, life went on its sleepy way, and Scout didn't have to confront the town's racial divide.
When Atticus mounts a real defense of Tom, the white community of the town is ruffled. His action breaks the code of whites sticking together and presenting a united front. According to this racist way of life, a white person who accuses a black person of a crime is always considered right just because he or she has white skin.
Because Scout has to overhear Atticus being called some ugly names and because of potential physical threats, Atticus has to talk to her more about race. Miss Stephanie, who shares Atticus's ideas about race and justice, also helps Scout grow in her understanding of the racial situation in the South.
In the courtroom, Scout perceives that Tom Robinson is innocent but is still convicted. This is also a lesson on racism for her.
Scout, too, becomes more aware of racism in her community when Calpurnia takes Scout to her black church. There, Scout sees how poor the black community is—but also how they stick together against the racist white society of Maycomb.

Scout first becomes aware of the racism in her community of Maycomb in the schoolyard, when Cecil, one of her young classmates, uses the racist term "niggers" to describe Atticus's client, Tom Robinson. She brings this incident home to Atticus, and he engages her in a discussion about the hateful word, and in this conversation with her father, Scout begins to understand the racist attitudes prevalent in her community.
Later, Scout and Jem have a difficult exchange with Mrs. Dubose about Atticus defending Tom, and she realizes then that these racist attitudes are completely "unfair." Jem and Scout then talk with Atticus about these attitudes in more detail, and Scout learns that from her father that using a hateful word like "nigger" is ignorant behavior.
As the trial approaches, more and more incidents like these two take place, forcing Scout to confront the reality of racism in her community.