Das Sex-Abitur (1978)

Anne is doing fine in most subjects, except that she sucks in French. Her bored housewife mum Eva is a dead ringer for her daughter, and she speaks French fluently - so the two swap places for the French classes. That swap stays in place for the subsequent homework class with Anne's friends, but Eva continues swapping with Klaus, Anne's boyfriend, and with Sven as well. That encourages Klaus to try out Sven's girlfriend Petra, and later, for good measure, the school's cleaning woman. Back in school, horny Eva also seduces the French teacher, and in the end the lot of them celebrate the successful exam with a big orgy - when unfortunately husband Heinz returns home early, and even more unfortunately with the headmaster as his special guest.