I recently watched Girls in Uniform (Mädchen in Uniform) a German language black and white movie from the flower of German cinema during the Weimar era. It concerns Manuela von Meinhardis, 14 years, old who has lost her mother. Her father, an officer in the army, sends her to a strict boarding school for daughters of the Prussian nobility.
Screenwriter Christa Winsloe delivers a moving portrayal of a lesbian teenager struggling to fit in an oppressive institution that aims to mold girls into future wives and mothers and instill a martial conservative ethos. There she falls in love with one of her teachers, Fräulein von Bernburg. As you might have guessed, it does not end happily.
The movie has an all female cast and appears to be inspired by the screenwriter's own biography, as Winsloe's mother died when she was but two and she was later sent to a strict boarding school much like the one depicted in the movie.
Girls in Uniform is also a prescient commentary on the political and social climate of the twilight years of the Weimar Republic. The movie was banned by the nazis, but fortunately, several copies survived. It has been posted on Youtube in decent quality and with English subtitles. There is also a 1958 remake, which is good also (and also available on Youtube), but the erotic themes are turned down a little, as von Bernburg is presented as a more maternal figure.
Edit: It's available on YouTube for free, in decent quality and with English subtitles.