This is a typical French coming-of-age movie, which means it differs quite a bit from the Hollywood/American model. First off, like a lot of French movies it is indeed pretty slow at times. While Hollywood movies tend to sacrifice realism for heightened drama, French movies often do the opposite, which isn't necessarily always a bad thing. This movie, however, seems to follow the formula of the infamous contemporary coming-of-age movie "To My Sister" (aka "Fat Girl") by being realistic, albeit slow-going, for most of the running time, but then throwing in shock ending that is as melodramatic (and unbelievable) as anything Hollywood has to offer. The jaw-dropping ending of "To My Sister" might arguably have been a fantasy of the troubled female protagonist, but that isn't the case here, and this climax is indeed pretty borderline risible.
French coming-of-age movies also tend to have much more nudity and somewhat more explicit sexuality than the Hollywood versions, even though the characters (and sometimes the actors) are a little shy of eighteen. This movie is no exception. Interestingly, the younger-looking character here was played by an actress (Karen Alyx ) who was actually in her early twenties, while the more developed-looking character was played by a 17-year-old Isild Lebesco (who even then had a body that would put any adult woman to shame). Both actresses do look kind of normal compared to your typical Hollywood prom queen types, but the much more voluptuous Lebesco has, not surprisingly, has gone on to a much longer career (Hollywood and France are certainly alike in that respect).
It also seems to be a conceit in about every French coming-of-age movie that an adolescent female character will inevitably become involved with an older (in some cases, MUCH older) male. I'm not sure why this is, but I think it has less to do with reality than wish-fulfillment--unlike most Hollywood teen movies, French coming-of-age movies have a substantial adult--and, especially, adult male--audience that this no doubt caters too. Anyway,the basic plot of this movie involves a pair of long-time teenage friends, one of whom, "Gwen" is maturing physically and sexually much faster than her friend. So feeling left out, the other girl, , tries to seduce her friend's father with very disastrous results for all involved. As with "To My Sister", however, this movie was directed by a woman and is told entirely from the perspective of the two young female protagonists (and if this were really a male fantasy, it probably would have been the sexier-looking "Gwen" who was involved in the lolita-esque affair and this affair would probably would have been a lot more consummated than it is here).
None of this is to say that this movie is necessarily bad, but it is certainly very typical of its kind.
