After Scout's first day of school, what is her assessment and what is her plan in To Kill a Mockingbird?
There is one more point Atticus makes that I'd like to add to the answer you already received (which is a good answer). We need to keep in mind that one of the things that upsets Scott is that Miss Caroline has told her that she has learned to read "all wrong"--because her father, according to Miss Caroline, doesn't know how to teach reading. Miss Caroline is a young and very inexperienced teacher (something Scout realizes in retrospect, as the adult Jean Louise narrating the story), but at the the Scout is threatened with the loss of the precious reading time she spends with Atticus. This isn't just about reading; it's about love, affection, and family time.
Atticus also cherishes this reading time together and understands that Miss Caroline, however wel meaning, is not necessarily right on this point. (Keep in mind that some of the things Atticus and Scout are reading are the newspaper and legal briefs.) He asks Scout if the understands what a compromise is, and then suggests a compromise of their own: If Scout will agree to go back to school, Atticus and Scout can keep on reading together every night, something they don't necessarily have to tell Miss Caroline.
To me, this is ironic in terms of what we now know about reading and the importance of parents reading to and with their children. Most teachers today would love to have their students' parents read with the children as Atticus does. We now know that this practice fosters a love of reading and greater learning. Miss Caroline didn't know any better and is dealing with a difficult teaching job. (Consder her encounters with the Ewell boy and Walter Cunningham.) Scout learns to be respectful and, as stated in the previous answer, to walk in another person's shoes.
After her first day of school (which is described in Chapters 2 and 3), Scout hates school. After dinner that night, she tells her father what her plan is. She says she will not go to school anymore. She says that she knows that her father never went to school. Instead, his dad taught him and his brother. So she figures her father can teach her too.
Although Atticus is sympathetic he of course tells her she has to go to school. He gives her some hints that she can use to be able to get along better with different kinds of people. This is where he talks to her about walking around in somone else's skin.