Assault (1970)

Synopsis
Someone is sexually assaulting and (usually) killing the students of a girls' school. There are entirely too many suspects to make the job of the Scotland Yard detective (Frank Finlay) an easy one. The girls' persistent use of the shortcut through the woods in which the crimes occur has only compounded the problem. Although one of the victims has survived the attack, shock has erased her memory of the event, and the detective's investigations are perforce guided by the vague impressions of the school's art mistress (Suzy Kendall), who witnessed something. ~ Clarke Fountain, All Movie Guide