Bourei Gakkyu (1996)

Bourei Gakkyu 1996 / 亡霊学級 1996 / ぼうれいがっきゅう , A Haunted School

A young girl wanders into a wing of her elementary school that has been abandoned for years and is rumored to be haunted. When she doesn't come back, a group of her classmates goes looking for her, only to find that they, too, are trapped inside. They must somehow find their way to safety, and quickly because the rumors of ghosts are turning out to be true. (Source: TMDb) ~~ Adapted from the manga by Tsunoda Jirou.