It's mentioned in "That Power" during the flashback monologue that as long as he's still on the bus, summer camp is still technically going on. The final lines of the song are "I got on the bus a boy. And I never got off the bus. I still havenít." Hence, if that metaphor is taken literally, that means he's still at camp (thus the album being named Camp even though most of the songs are set after he grew up and became famous) and if he's still a boy then he's still childish.
The monologue also explains his disconnect from actual relationships throughout the course of the album (especially on "Kids (Keep Up)," "Heartbeat," and "L.E.S.").
Camp begins and ends at the exact same place. "That Power" ends with a thirteen-year-old Donald returning to his life in the city, which is where "Outside" begins.