In "To Kill a Mockingbird" chapter 12, what does Scout learn at the First Purchase Church about Black people's lives?

Scout gets a great first-hand lesson on the lives of Maycomb's black citizens when she and Jem accompany Calpurnia to her church in the Quarters one Sunday when Atticus is out of town. She immediately discovers that Calpurnia wants everyone to be proud of her guests: Calpurnia bathed Scout more "roughly" than ever before--"She made me soap all over twice"--and made her "wear a petticoat" and "a pink sash." The black members of First Purchase Church showed the children deep respect,

... the men stepped back and took off their hats; the women crossed their arms at their waists, weekday gestures of respectful attention.

All but Lula, that is. Lula objected to "white chillun here," and her aggressive nature made Scout want to go home. But the other members soon "created a solid mass of colored people," forcing Lula into the background. The children were personally greeted by Reverend Sykes, and once inside the church, Scout discovered a new wealth of information:

• The inside was "unceiled and unpainted."
• There was no organ, piano, hymnals or bulletins.
• There were no hymnals because few of the congregation could read.
• They sang their songs by "linin'," with Zeebo (Cal's son) reading each separate line, followed by the congregation repeating and singing them--"miraculously on pitch."
• The collection was taken in a "black enameled coffee can."
• Tom Robinson and his family were members.
• The church was used as a gambling house by white people on weekdays.
• Calpurnia spoke quite differently with her friends than she did in the Finch home.

In "To Kill a Mockingbird" chapter 12, what does Scout learn at the First Purchase Church about Black people's lives?

Scout and Jem learn quite a few things.

First, they learn that the black church is much poorer than their own.  They see that they don't have hymn books and church bulletins and such.  They probably should have figured the black church would be poorer, but they didn't.

More importantly, they learn that some parts of the black community resents white people and wants them to stay in their own place.  Also importantly, they learn that the black community expects its members to act like they are black  -- this is why Calpurnia speaks like a black person while she is among other black people.

What do Jem and Scout learn about the black community during their visit to First Purchase Church in To Kill a Mockingbird?

In To Kill A Mockingbird, Calpurnia provides Jem and Scout with the  rich experience of connecting the two worlds of blacks and whites:    

Calpurnia, the Finch’s black housekeeper, provides a link between the black world and the white world in which the children move. She is a constant in their lives and fills a mothering role in the absence of their own mother. As a wise and loving black woman, Calpurnia provides the children with an experience which guards them against being drawn into the racist attitudes of the majority of their society.

One way that Calpurnia connects the different worlds of the blacks and whites is by taking Jem and Scout to her all black church. During the 1930s in Alabama, black people and white people did not attend church together. Whites had their own church and blacks had their own church. During this novel, Jem and Scout learn about the racial differences when they visit Calpurnia's all black church. Jem and Scout learn what it feels like to not be accepted based on skin color. Some of Calpurnia's black church members do not welcome Jem and Scout because they are white. Some of the black church members insists that Calpurnia should not have brought the white children to her black church. Lulu is rude to the children. She insults Calpurnia for bringing the white children to an all black church. Calpurnia takes the white children to her church because she expects her black church members to accept Jem and Scout, even though they are white. 

 While visiting calpurnia's church, Jem and Scout notice that Calpurnia talks differently with her black church members. Jem and Scout see that blacks and whites have different lives. Calpurnia uses a different dialect with the black church members. Calpurnia uses relaxed English with her church family. When working at the Finch family's household, Calpurnia uses standard grammar.

Clearly, Jem and Scout observe the differences between blacks and white while visiting Calpurnia's church. Also, Jem and Scout learn that Calpurnia's black church cannot afford hymnals for everyone. Jem and Scout learn about the inequalities of blacks who cannot afford the luxuries that white people enjoy. Truly, blacks are discriminated against and Jem and Scout witness it first hand when they visit Calpurnia's church.  

Calpurnia takes Jem and Scout to her church because she does not discriminate. Sadly, Calpurnia learns that some of her church members are just as discriminating as the whites. Clearly, Lulu does not think it is fair for white children to be allowed in a black church because black children are not allowed in a white church. 

What do Jem and Scout learn about the black community during their visit to First Purchase Church in To Kill a Mockingbird?

Their visit to church with Calpurnia is eye-opening. This is the first time they see her in her element. Jem and Scout are used to the way Calpurnia acts and talks in their home, and now they are able to see her when she is with her own people. They are especially surprised by the way that she talks- with the southern black dialect that she could feel comfortable using only around people with whom she was comfortable.

What does Scout learn about the lifestyle of black people in To Kill a Mockingbird?

The passages that you are looking for can be found in chapter 12, where Calpurnia takes Jem and Scout to her church, because Atticus is out of town.  During their visit to Cal's church, Scout is startled and intrigued by many new facts that arise.  She finds out, first of all, that Calpurnia changes her dialect whenever she is around her black friends.  When she is at Scout's house, she talks like Scout and Jem talk, but when they arrive at the church, Cal changes her speech. When she questions Cal about this, Cal states,

"if I talked white-folks' talk at church,...they'd think I was puttin' on airs to beat Moses."

The next thing that Scout learns is that most of the black people attending the church cannot read or write.  She wonders about this as they are about to sing a hymn, and can't find a hymnal; she asks, "How're we gonna sing it if there ain't any hymn books?"  She soon learns that Zeebo-who can read-sings out one line that everyone else then echoes.  A couple other startling facts:  Scout realizes that Tom Robinson's wife is having a rough time since Tom is in jail, and that the people of her church are helping her out through monetary donations.  She also learns that Cal doesn't know how old she is, because of black people being illiterate and not taking much stock in a calendar.  She also learns, through the impertinent comments of Lula, that some black people don't really welcome white people in their neighborhoods.  So, Scout learns an awful lot in the couple of hours that she is at Calpurnia's church, and takes it all in with her usual curious questions.

What new things does Scout learn about how the African American community lives?

I am assuming you are either referencing chapter 12 or 15.

In chapter 12, Scout and Jem go to church with Calpurnia. They operate church more passionately with a lot less. They take care of their own (as demonstrated by the locked doors to take a collection for Helen Robinson). They sing based on one literate person's ability to read an old hymnal and they line the words. They welcome Scout and Jem with open arms... all except for Lula who demonstrates her racism.

They dress so well for church and they smell amazing. This shows their respect for their faith.

Throughout the rest of the book, there are times when the black community shows their respect and appreciation through gifts of food. In chapter 15, the kids watch the Negro community eat on the lawn before the trial starts.

What new things does Scout learn about how the African American community lives?

It is hard to know which part of the book you are talking about, so I will talk about some things that Scout learns about the black community in Chapter 12, when she and Jem go with Calpurnia to the First Purchase Church.

Mainly, she learns that black people have a certain amount of pride and expectations of how each other should act.  She finds out that some black people do not want her and Jem at "their" church.  She finds out that the black church lacks money for hymn books.

But what I think is most important is how she learns about black expectations of one another.  She learns, for example, that Calpurnia talks differently among black people.  This surprises Scout because she does not realize that the African American community has its own ways and is proud of those ways.