The Haunting at Thompson High 2005 on netflix

Three students stay after class for detention. After a while they realize they were left alone, and the doors to the school have been chained up. They find out they have a connection to one another. Each has a history bullying a student by the name of Elliot Maggin, who took his own life because of bullying. After strange events happen, they realize they are not alone. Elliot is with them. Written by BiGMaN -SeveredHorror.com