I doubt you can name this ...
Question: I doubt you can name this movie, but it was made in the '60s or '70s and is about an all-girls school where the female schoolmaster's preteen son is killing the girls. The movie ends with a scene in which the son is admiring an old skeletal corpse — with hair — of one of his victims while the mother is screaming in the background. It might have been European.
Answer: Oh ye of little faith! You're describing the 1969 Lilli Palmer film La Residencia, released in the U.S. as The House That Screamed; it's also played under the titles The Boarding School and The Finishing School, which give a clue as to the setup: The German-born Palmer, who began her career in European mainstream films but quickly slid into a long run in horror and exploitation pictures, is the strict headmistress of a Spanish school for wayward girls where the usual Euro-horror stuff starts happening. It doesn't seem to be commercially available on DVD or video in the U.S., though it is available as a PAL DVD from a company called Eurovista. Do not mistake the ultracheap Hellgate: The House That Screamed 2 for a sequel. It's not.