What is the most important thing Cal wants Scout to learn in To Kill a Mockingbird?

The Finch family housekeeper, Calpurnia, teaches Scout many things during the course of To Kill a Mockingbird, but the visit to Cal's church may have been one of the most important....

In the book "To Kill a Mockingbird" Calpurnia is representative of a mother figure for the children. There are two things that are significant that Calpurnia teaches Scout.  Walter Cunningham goes to the house for dinner and pours syrup over everything.  Calpurnia scolds Scout after she rudely announces that Walter is pouring syrup over everything.  Calpurnia is trying to teach Scout to be good to people and not to say rude things.

This is reflected again when Calpurnia takes Scout to her church in the colored community.  The church was built by freed slaves.  Scout notices that Calpurnia uses different types of speech and communication with her black friends than she does around white people.  Once again Scout rudely asks her about it.  Calpurnia answers her but also lets Scout know that one can not always say what one wants to say and her behavior was rude.

However, the greatest thing that I believe Calpurnia teaches Scout through her guidance and taking her to the black community is that black people are just like white people.  They have families, faith, and dreams.  They are a community that works together to survive.  She teaches Scout the existence of humanity as being one and not a separate color.