What do the children learn about people and social class in Chapter 16 of To Kill a Mockingbird?

Chapter 16 tells of Jem and Scout heading to the Maycomb County courthouse where Tom Robinson will stand trial for rape. When they reach the courthouse square, they note the "gala occasion" taking place. Large groups of men, women, and children are gathered in an almost party-like atmosphere enjoying their lunches where soon after a black man will be on trial for his life. As the children take in their surroundings, they are the learners of many lessons on social standing in their community.
The children notice that the more "affluent" townspeople are drinking Coca-Cola with their lunch. The "negroes" are situated in a corner of the square where they are also eating, but it is important to point out that they are doing so more quietly than the others. The reader gets the impression that black people are tolerated as long as they remain quiet and know their place. The children then have a conversation about Mr. Dolphus Raymond, a white man, that prefers to sit with the black people. According to Jem, Mr. Raymond sits with them because he likes them better than white people. His choice affects his social standing with white people. Jem then explains the unique situation of the "mixed chillun." He refers to them as being sad because they don't belong anywhere. They are "in-betweens," accepted by neither white people nor black people.
As the children enter the courthouse, they overhear a conversation about Atticus, their father. Atticus has been criticized for defending Tom in court. One gentleman points out that Atticus is only defending Tom because he has been appointed to do so. However, the other responds that he doesn't like that Atticus actually plans on defending him. In other words, going through the motions of doing your job is one thing, but actually attempting to defend a black man in court is something else entirely.
Social standing is maintained inside the courtroom as well. Once the white observers enter, the black people begin to enter the courthouse where they take their seats in the "colored balcony." With nowhere left to sit, Jem, Scout, and Dill go with Reverend Sykes to this balcony where four black people allow them to take their seats. Society dictates that they must accommodate for the white children.