...And Give Us Our Daily Sex (1979)

erónica and her friend are two very sexy bisexual nurses who live upstairs from a rather boring couple and their teenage son. In a science class at school he learns how to build a periscope, and uses it to spy on the nurses sexual antics. Meanwhile, Albert's mother is being even naughtier than her precious boy, sneaking off for some extra-marital sex while her hair-obsessed husband is at the salon, having his follicles tended to. (imdb)