Scout declares early in chapter 2: "I never looked forward more to anything in my life" (15). Unfortunately, Scout is going to learn a lot in this single day. By the end of the day Scout is loathing every second of the first grade.
Scout has learned some very important lessons. She has had the point driven home that she is quite different from her peers. While in some ways this is obvious to her (she is able to eat a good meal for lunch and baths regularly and can afford proper attire), it is also obvious to her in other ways that she was not aware of (she can read at an advanced level). Scout cannot fathom why her teacher is so upset at her ability to read, nor can she fathom how her teacher wants Atticus to stop interfering with her learning.
Scout ends the chapter observing Miss Caroline crying at her desk. Because of Miss Caroline's behavior toward her, Scout never wants to return to school again. In this Scout is given a wake up call to the fact that the world does not always meet her expectations. She has lived a sheltered life with Atticus. But the looming trial will reinforce many of the lessons Scout was exposed to during her first day of school, such as Miss Carolin unfairly persecuting Scout for being able to read or for speaking out when she is only trying to help, foreshadow the same unfairness of the Robinson trial.
At the beginning of Chapter 2 in To Kill a Mockingbird, Scout was excited about starting school. When she got to school, however, the teacher, Miss Caroline, found out that Scout could already read. Miss Caroline told Scout that Atticus was teaching her the "wrong" way to read, and that it would be better if he didn't teach her anymore. This made Scout angry, and she told the teacher that her father had not taught her to read and that, according to Jem, she was born reading. The day only gets worse when Scout tries to explain to the teacher why Walter Cunningham won't accept a loan of lunch money, and the teacher swats her hand with a ruler for speaking out of turn. This action makes the other kids in school laugh at her. As a result of this miserable first day, Scout vows never to return to school.