Fortress is a 1986 criminal and survivalism drama thriller directed by Arch Nicholson and written by Everett De Roche.
A teacher Rachel Ward and her students at a small rural school in Australia are kidnapped and held for ransom by a band of violent shotgunwielding masked thugs wearing Christmas character masks. Held for ransom in a cave, she and the children daringly escape from their captors, are pursued, establish a stronghold, and fight for their lives.The film is based on Gabrielle Lords novel of the same name, which was loosely based on the 1972 Faraday School Kidnapping. ........
Source: Wikipedia