Documentarian Robert Greene chaperones 18-year-old Kati Genthner through the three days before her graduation (with honors) from Pleasant Valley High School near Jacksonville, Alabama. She is preparing to leave for the comparatively cosmopolitan Charlotte, North Carolina, where her out-of-work parents have preceded her. In their absence, she has clung to boyfriend-turned-fiance James, who shows a pulse but is otherwise an unambitious live-at-homer. Greene, Kati’s elder half-brother, meshes with the surroundings enough to play fly-on-the-wall, establishing his outsider-aesthete status by rendering her existence in ethereal atmospherics and post-rock soundtrack. (The subject’s native music suffices: tuneless marching bands, muttered chorales, cheeseball “soaring” radio rock.) Without belaboring any point or entrapping his subjects, Greene—whose film is repetitive even while detailing such a brief period of time—suggests Jacksonville’s social options as recombinations of TV room, mall, backyard pool, church, and public school. (The other time-passer is the elephant in the room: s-e-x.) Throughout, perspectives on the film’s present are offered via the past (footage of a lively 8-year-old Kati) and the future (Kati’s narration, sober with pee-test revelations, recorded two months after filming). Greene may intend Kati’s story as a quiet tragedy, but the native feeling of that’s-just-the-way-it-is lethargy (“Only in Alabama can you be a home-school dropout”) is rather convincing.