The Substitute: Failure Is Not an Option (2001) on Netflix

Plot summary

Karl Thomasson, who once served in Special Forces and later worked as a mercenary, takes on a mission from Teague, an old army friend. Teague's nephew Ted is a cadet at a Georgia military academy the General helps fund, and Teague believes cadets and faculty there have joined a neo-Nazi group called the Werewolf Unit, officially a special unit at the school. Karl goes undercover as a history teacher. He argues with Buckner, a cadet who dismisses historical accounts of the Holocaust, and finds an ally in Devlin, a martial arts instructor who served with him. He also meets Jenny, the academy doctor. The unit has backing among the academy's officers as well.