The Haunting at Thompson High (2006)

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.