Atticus tells Scout that she needs to look at things from Miss Caroline’s point of view.
Scout is very excited about starting first grade. For years she has been watching Jem go to school while she has to stay home and miss all of the fun. However, school is not at all what Scout expected. She gets in trouble almost immediately for being able to read.
[As] I read the alphabet a faint line appeared between her eyebrows, and after making me read most of My First Reader and the stock-market quotations from The Mobile Register aloud, she discovered that I was literate and looked at me with more than faint distaste. (Ch. 2)
This is very disturbing to Scout. She loves reading as much as she loves breathing, and although Miss Caroline tells her that her father has taught her incorrectly, he actually didn’t really teach her. She learned to love reading because he loved reading. She followed along with him as he read, whatever he happened to read, and soon she could read it too.
When Scout complains to Atticus that night about her unfair teacher, he tells her that she needs to learn to see things from Miss Caroline’s point of view. Miss Caroline learned as much on the first day of school as Scout did.
She had learned not to hand something to a Cunningham, for one thing, but if Walter and I had put ourselves in her shoes we’d have seen it was an honest mistake on her part. We could not expect her to learn all Maycomb’s ways in one day, and we could not hold her responsible when she knew no better. (Ch. 3)
Miss Caroline is not from Maycomb, which made most of the children suspicious of her. She also is a brand new teacher, and very young. Atticus knows that there will be a bit of a learning curve for the teacher as well as for her students. They will need to get used to her educational strategies, and she will have to get used to their Maycomb methods.
Scout is actually learning an important lesson in empathy. She is young enough to still be figuring out the world. Atticus is trying to help her understand that she needs to try to see another person's perspective on things before judging the person. Throughout the book, Scout will continue to work on this lesson as she grows up.