In their childish innocence, Jem and Scout are surprised to find that only four people in Calpurnia's church can read. They have no understanding that for the most part, Maycomb's black population is denied an education. In fact, when Calpurnia remarks that black people don't age as quickly as white people, Jem seriously suggests, "'Maybe because they can't read'" as though reading is a burden that not everyone needs to shoulder. Lee uses the children's ignorance to underscore the injustice African Americans receive in all aspects of their lives. All white children — even the Ewells — are afforded the opportunity to learn to read. Scout and Jem's surprise helps readers understand this unfairness at a deeper level.
Remarkably, Calpurnia doesn't lament the African-American position in Maycomb society or try to explain prejudice to the children. Instead, she simply answers their questions, and lets them figure out the rest. When Scout asks to visit Calpurnia at her house, Calpurnia doesn't go into a dissertation about how white children generally don't spend time in black people's homes, she just smiles and says, "'We'd be glad to have you.'"
Ironically, Aunt Alexandra holds many of Maycomb's prejudices against blacks. She has an African-American chauffeur, and says "'Put my bag in the front bedroom, Calpurnia'" before she even says hello. The fact that Jem insists on taking the bag shows both maturity and lack of prejudice on his part. Still, Aunt Alexandra's various prejudices cause Scout to comment "There was indeed a caste system in Maycomb, but to my mind it worked this way: the older citizens, the present generation of people who had lived side by side for years and years, were utterly predictable to one another." Later in the novel, Scout will redefine Maycomb's caste system as she discovers that even living "side by side for years and years" doesn't make human nature predictable.
