eleased a decade after Hausu, Hyôryu Kyôshitsu is a live-action adaptation of Kazuo Umezu’s manga of the same name, which was serialised between 1972 and 1974. The story in both the manga and the film concerns the mysterious transportation of an entire Japanese grade school—and all within—to a foreboding desert wasteland. As the story unfolds, the diminishing student body weathers this apocalyptic crisis while searching for clues about their surroundings, and dealing with psychological breakdown and dangerous exterior forces. (from: http://waxmask.blogspot.de/2010/07/drifting-classroom-hyoryu-kyoshitsu.html)

Overview from themoviedb.org