'Satan's School for Girls' (1973) - David Lowell Rich. 

Aaron Spelling's cult Satanic-panic TV shocker opens in a spooktacularly sinister manner with the plainly distressed blond beauty Martha Sayers (Terry Lumley) alighting in a greatly distressed state at her sister Elizabeth's suspiciously empty house. The especially evil occult plot is galvanized by Elizabeth (Pamela Franklin) returning home only to discover to her boundless horror that her younger sister hung herself in the living room! Resolutely unwilling to accept the coroner's report of suicide, plucky Elizabeth enrols in her sister's highly regarded college under a false moniker in an attempt to surreptitiously Scooby Doo the dark skinny over the grisly event.

Once covertly ensconced in the diabolic enclave of Salem Academy for Women the remarkably sure-footed filmmaking by ace director David Lowell Rich ekes the most out of A.A.Ross's classy, nimbly-paced script creating a suitably paranoid, neo-Gothic atmosphere, full of furtive, twist-headed, screwball teachers, hysterical ingenues, and myriad, macabre cryptic clues all wending inexorably to the school's diabolically dank basements; with its secret medieval portal protecting a crepuscular antechamber and, perhaps, discovering that the dastardly origins of these unearthly deaths are quite possibly being manifested from the mephitic bowels of hell itself! 

The joyful fact that 'Satan's School for Girls' remains one of the more profoundly engrossing, fondly remembered TV movies from the 1970s is, perhaps, largely due to the thrilling film's splendid performances, cogent script and really terrific score by maestro Laurence Rosenthal, which also strongly suggests that the shadowy, satanic shenanigans of these sin-saturated sisters shall continue to draw avid terror fans into this stifling vortex of black-hearted witchery for many, many years to come!