Scream Girls (2008)

According to an urban legend, a girl named Hikiko Mori was taunted and bullied relentlessly by her classmates, eventually resulting in her accidental death. Holding a grudge against all bullies, her spirit now haunts her former school, slowly gathering the strength to exact vengeance on the living. A group of frightened school girls decide to investigate the rumors further and what they find convinces them that they have to stop the spirit of Hikiko-san before it's too late