This is about as cliche as one can get. Two girls meet in a boarding school and fall in love.

https://www.imdb.com/title/tt0063683/

A older woman visits the boarding school of her youth after a 20 year absense. While strolling about the deserted grounds and classrooms she remembers her highly emotional experiences there, and well-executed flashbacks occur to her youth. At 17 she is abandoned by her loving mother because of remarriage and left at a European boarding school, disenchanted and lonely. Immediately she meets Isabell, an older, confident, rebellious girl. The two develop a friendship quickly without much conversation or bonding, but have the always temporary chemistry necessary for their friendship to progress into a sexual relationship. The sex scenes are slow and sensual -as they should be for two young girls experiencing lesbianism for the first time. Despite their undying love confessions to each other, Theresa wakes up one morning to find Isabell has left the school, her room and desk replaced with another student. She never see's Isabell again.
If not for the quality of photography this would be a total snoozer.

I tried to find a clip but for some reason youtube listed the best clip as age restricted. Not sure why the movie is completely tame except for verbal descriptions of sexual activity.