Aoi sanmyaku

In this 1949 film, Setsuko Hara is Miss Shimazaki, a modern, liberated, proto feminist teacher who assures her pupils in an all girl high school in a small town in Japan that is OK for girls to be dating boys and not something immoral, as traditional cultural mores before the war would indicate. Not everybody in the conservative community will like her message, though.

A bit melodramatic, dated and didactic (it openly condemns "feudalism" of traditional Japanese society and encourages individualism), but fascinating. This was considered one of the best Japanese films of 1949, along with Late Spring (which has aged much better). That same year there was a sequel of this film, called New Blue Mountains and with the same director and cast.