Scout learns that First Purchase doesn't have hymnals. They all "line" when they sing. Most of them can't read anyway, but they couldn't really afford the hymnals like her church has. The other shocking piece of information comes from Cal's "double life."
"That Calpurnia led a modest double life never dawned on me. The idea that she had a separate existence outside our household was a novel one, to say nothing of her having command of two languages."
Scout was shocked to hear that Cal knew how to speak very clear and proper English, but around her friends and church members, she didn't want to appear "high and mighty" so she spoke slang and broken English like they all did.
Scout also learned that they weren't welcomed by all of the church members. Lula showed that side first. She didn't understand why Cal would bring white kids to her church.
"You ain't got no business bringin' white chillun here--they got their church, we got our'n."
So Scout and Jem both see how if feels to be on the other side of the situation. Where most times the whites treat the blacks with disrespect, she got to see how it truly felt.