The Substitute 4: Failure is not an option.
(2001)

Retired mercenary, Karl Thomasson (Treat Williams) is asked by his old friend, Colonel Teague, to inquire about his nephew Ted, who goes to a private military academy run by Brack (Patrick Kilpatrick). Thomasson goes undercover as a teacher, only to discover that Brack is recruiting from the school for a white supremacist army called The Wolverines. Brack's influence begins to slip when one of his cadets dies on a mission. In response to the threat Thomasson brings, he has Colonel Teague murdered.

When confronting Jenny (Angie Everheart) about her potential involvement, she and Thomasson are found by Brack who tries to kill Thomasson. However, Jenny pushes Thomasson out of the way and is killed instead. Thomasson follows Brack to a courtyard and Brack orders Ted to hold a gun to Thomasson's head. Thomasson then reveals to Ted that Brack had his uncle killed, Ted, several other Wolverines (who finally reject Brack's philosophy), and other cadets then point their guns at Brack ,realizing how insane he really is. When Brack tries to strike Thomasson with a saber, the cadets gun him down.

The film ends with Thomasson and Luther (Bill Nunn) wheeling a recovering Delvin (Tim Abell) out of the hospital. Thomasson reveals he will be temporarily taking over the academy until the trustees find a new commandant for the school. 

Thanks Spectre!