After going to Calpurnia's church, Scout states, "That Calpurnia led a modest double life never dawned on me." In what sense does Calpurnia lead a double life?

Answer: The fact that she had a separate existence outside their household.

Explanation: At the church, the children learn that Calpurnia is much older than she looks and is one of only four people in her church who can do so, that she taught Zeebo her son how to read as well and that she knew their grandfather. They found out that she grew up at Finch's Landing and were greatly surprised that she could speak the dialect of the members of her church.

Scout is very impressed with her modest double life as well as her command of two languages. Tjis made the children see Calpurnia in a new light andprompted Scout to ask if she could come to her house sometime.