At the night before Final Battle against Kuromorimine Girls High School on episode 10, all girls from Usagi Team are seen watching a movie, and it looks like a movie about tank.
What movie was it?
They were watching Kelly's Heroes. It's an old war movie in 1970 about a group of American soldier who tried to rob a bank far behind enemy line.
While the original poster looks different, it match with Japanese poster for the movie
The scene they were watching is around 1:56:00 when Oddball and Kelly, the main character, shoot down a Tiger, the same tank with Kuromorimine's tank.
Notes: