It's a little hard to describe this movie. It's kind of like "American Beauty" where you have a dysfunctional middle-class family with a father that lusts after his teenage daughter's best friend, but in this movie he actually has sex with the friend (repeatedly)and perhaps his own daughter as well(?!) To be fair, this movie is nowhere near as offensive and disturbing as it sounds on paper. It's directed with subtlety and some amount of class; it's much close to Italian art than Italian sleaze. The actors playing the mother and father are both very good, and the two teenage girls are played by Ornella Muti and Eleanora Giogi, both then in their late teens/early twenties, and two of the most beautiful women in the history of the Italian cinema. (Like Jenny Tamburi in the similar film "La Seduzione" or Gloria Guida in about every movie she ever made, these two look good both in and out of their schoolgirl uniforms, but that is not because they are remotely believable as actual schoolgirls).
This movie is not so much offensive or disturbing as it is confounding. The Muti character's mother who was once a famous concert pianist is suffering from some kind of mental breakdown, and her father is understandably drawn to a new life with the younger Giorgi character, who is like a sexy blank slate for all his middle-age fantasies. The motivation of the younger characters though are much more opaque and they are rather thinly-drawn as characters. Giorgi's character clearly lacks for parental attention, which explains why she befriends her friend's sickly mother, but not why she throws sex on her father several times but otherwise gives him the cold shoulder. The Muti characters actions, however, are completely perplexing: she is having trouble losing her virginity (which in itself strains credibility to the limit), but comes up with the most jaw-dropping and unbelievable solution to her problem imaginable.
This movie is available in two versions: an Italian version which censors out the full-frontal nudity (which is hardly the most offensive thing in this movie), and a badly-dubbed English which is very confusing and seems to leave out a lot of plot points.
Oh, and by the way, Agostina Belli is NOT in this movie. (Muti. Giorgi, AND Belli all in the same movie probably would have melted the celluloid in the camera). I'd recommend this movie to fans of beautiful Italian actresses, but be prepared to possibly be offended and definitely confused!