The speaker sets autumn beside their own life, and the two keep mirroring each other. Leaves change color; the speaker changes grades. Trees go bare; the speaker is "baring less," which suggests becoming more guarded or private as they grow older. Birds migrate south, and the speaker migrates toward friends and away from parents. Nature's seasonal shifts become a way of describing the ordinary, slightly unsettling process of growing up.
The short, clipped lines in the first half feel like quick observations, almost a checklist. Then the poem softens. Falling, standing and flying, which first described leaves, trees and birds, are claimed by the speaker, now tied to Ashley, Andrea and James. Falling is no longer sad, because it means falling toward people who matter. The mood is warm and hopeful, with a teenager's big promise at the end: "for always and eternity." The speaker seems sure that these friendships will last, and the poem lets that certainty stand.