August explains that in the spring, the Beecher Prep fifth graders go away to a nature retreat for two nights. Everyone is excited about it, but he's not super excited because he's never slept away from home before. When he was about eight he and Christopher almost had a sleepover but at about midnight, August panicked. Lisa called Mom and Dad and they came and got him. August says that this is all he's worried about; he's actually really excited.
The balance between feeling nervous and excited suggests that while this is a new and scary rite of passage for August, he's ready to face it now in a way that he wasn't when he was eight. This makes it clear that he's growing, developing, and becoming more independent as he moves towards adulthood.