Jean Louise catches Walter Cunningham in the schoolyard and beats him up for being the reason she got in trouble, but Jem stops her.
She explains to Jem (who calls her Scout, so we will too) what happened.
Jem invites Walter to come home for lunch with Scout and him.
At the Finch house, Atticus talks to Walter about farming, while Jem and Scout listen half-comprehendingly.
Walter asks for molasses, which he proceeds to pour all over his food.
Scout is all, "What?," and he stops in embarrassment.
Calpurnia calls Scout into the kitchen, where she gives her a lecture on hospitality—Walter's a guest and so he can basically do whatever he wants.
The kids go back to school, and Scout grumps silently about Calpurnia's lecture.
She's called back to the here and now by a shriek from Miss Caroline, who's seen a "cootie" (3.37)—probably a louse, which may sound more familiar in the plural, lice—on one of the students.
Miss Caroline tries to send the student, named Burris Ewell, home to wash his hair (after looking up lice remedies in a reference book), and says he should take a bath (which he apparently really needs, since he looks worse than Pigpen from Peanuts) before coming back to class.
But Burris tells her that he's not coming back.
What? Apparently, Burris is one of the Ewells. Ewells come the first day to satisfy the truant officer and then skeddaddle.
Burris decides he's already done with school for the year even though the first day isn't over yet, and manages to make Miss Caroline cry before he leaves.
The other students try to cheer Miss Caroline up, and she reads them another boring story.
Highly dissatisfied with her first day of school, Scout goes home and makes plans to run away.
Atticus comes home from work, having apparently forgotten about Scout's lunchtime misbehavior, and Calpurnia gets back on Scout's good side with tasty crackling bread.
After dinner, Atticus invites Scout to come read with him, which brings up unpleasant memories.
Scout tries to convince Atticus that she doesn't really need to go to school, but he's not buying it.
She tells him about her first day of school, and Atticus tells her to try to think about things from the other person's perspective—in this case, Miss Caroline, who was only trying to do her best in a strange place, whose ways she doesn't yet understand.
Scout says that Burris Ewell stays home from school so she should be able to do so too, but apparently what holds true for Ewells doesn't apply to Finches.
Finally, Atticus proposes a compromise: they'll keep reading at home if she'll keep going to school—but she shouldn't tell Miss Caroline about it.