Although Scout and Jem are facing larger conflicts with society, they still live the lives of children and have conflicts with each other.
In this episode, Jem and Dill are explaining to Scout why they need to sneak onto Boo Radley’s porch to peek inside. Boo Radley is the neighborhood monster, and the ones all the kids are afraid will come out of his hiding place and eat them. Jem tells Scout why they have to do it at night.
Because nobody could see them at night… because if Boo Radley killed them they'd miss school instead of vacation, and because it was easier to see inside a dark house in the dark than in the daytime… (ch 6, p. 37)
This quote is an example of a brother and a sister arguing, as brothers and sisters do. Scout IS a girl, but she is a tomboy largely because she spends a lot of time with her brother. If Scout had been raised by a mother with sisters, she might have turned out differently. Instead, Jem was her main influence. However, she also spent a lot of time with Jem. When family members spend a lot of time together, they sometimes get on one another’s nerves.
Just as people don't always agree, family members don't always agree. Everyone thinks he knows what is best for family members. Scout wants to protect Jem, and it annoys him. Also, conflict between brothers and sisters is a part of growing up.