Detention (2003 film)

Detention is a 2003 action film directed by Sidney J. Furie. It stars Dolph Lundgren as a soon to be retired high school teacher Sam Decker who has one last detention to proctor and Alex Karzis as Chester Lamb. Unfortunately, drug runners have chosen to attack the school. Sam must band together the trouble makers and misfits in detention to defeat the criminals and stay alive.

Led by the brilliant and sadistic Chester Lamb Alex Karzis, the invaders are surprised to discover that Sam and the kids from the detention room are still inside the school.The hunt is on as Lambs henchmen ruthlessly stalk the teacher and students through the schools halls and classrooms, while Lamb tracks them on the surveillance cameras, turning the schools security system against his prey. ........

Source: Wikipedia