The purpose for chapter 26 is to explain how the people of Maycomb are hypocritical, and that Jem is still having trouble dealing with the racism all around them.
Chapter 26 describes Scout’s third grade teacher Miss Gates and a lesson in current events. Cecil Jacobs has an article on Hitler rounding up Jews, and he feels it is wrong for him to do it just because they are Jewish. Miss Gates agrees. This puzzles Scout. She does not understand why people can be so hypocritical as to hate Negroes when they blame others for hating Jews.
Scout asks Jem what is the matter with people. She heard Miss Gates coming out of the courtroom after the trial.
I heard her say it's time somebody taught 'em a lesson, they were gettin' way above themselves, an' the next thing they think they can do is marry us. Jem, how can you hate Hitler so bad an' then turn around and be ugly about folks right at home-" (ch 26)
Jem gets very angry, and Scout does not understand why. Atticus tells her Jem is trying to forget something. Scout does not yet understand how much the trial affected Jem. He feels just like she does about people being hypocritical, but for him the grief is still too near. He can’t talk about racism, because he is still stinging from the realization that Maycomb is not a “cocoon,” and there are racists everywhere.
In a way, this chapter establishes how difficult it is to grow up for each Finch child. Scout is trying to understand how the world works, and Jem has had a hard lesson in it, and is thus trying to forget how the world really works.