No good will come of this. We know it. We've been educated over the years to instinctively know it. When a charming 35-year-old man in a shiny sports car pulls alongside a 16-year-old schoolgirl and offers a lift, our first reaction—honed by years of dreadful police reports and popular horror tales—is to yell “;Run!”; at the screen.

But this is 1961, in a suburban west London, and this chap isn't interested in dismembering girls, he's just interested in acquiring a girlfriend.

And Jenny is bright as a penny, cute without being beautiful, studying hard to gain Oxford admission, smart enough to wonder about the strangely sophisticated world out there—a world seemingly removed from her parents' comfy flat on a cobblestone street.

It's the '60s before it began to swing, and so Jenny's imagined sophistication runs to things French. She blurts out random phrases in Gallic, mostly confusing those around her; she sings along to French pop songs. She's a flower waiting to be picked.

David, the older man, is funny and terribly polite and actually interested in her and something of a wonder when it comes to getting his way. And he's in no hurry. To seduce Jenny, first he seduces her doting parents. Before long, sending their teenage daughter off to a louche weekend in Paris with this man seems like their own idea.

Nothing good will come of it, no error, although in this painfully funny, sharply realized cautionary tale, lessons are learned the hard way, through the heart instead of the brain. Simply growing up is an education, although an Oxford degree will open doors that a teen romance never will. Things haven't changed that much.

Based on a memoir by British journalist Lynn Barber and insightfully expanded by novelist Nick Hornby—who turns tart dialogue into an art form—“;An Education”; is something of a wonder in the way it evokes both the atmosphere and climate of a nascent stage in modern times, a world on the cusp of mass communications and public intimacy, reflected in the shining eyes of Jenny.

Played by Carey Mulligan in a star-making turn, Jenny may be using her older beau as much as he is her—and, as David, Peter Sarsgaard is no lecher, although he is every inch a confidence man.

He genuinely cares for Jenny, sees in her the promise of a life better lived. Interestingly, as Jenny grows wiser, David becomes curiously infantile. Both of these actors are in top form: Although Mulligan is the bright light here, Sarsgaard is not in her shadow. He actually gives a very sad, subtle performance, compared with Mulligan's showy incandescence.

They are surrounded by perfectly cast second bananas.

Alfred Molina and Cara Seymour as Jenny's befuddled parents; Dominic Cooper as an elegant, light-fingered pal of David's who is surprisingly sensitive; Rosamund Pike as a good-natured party girl who's not at all educated but doesn't give a damn; Olivia Williams as Jenny's English teacher, a probably repressed lesbian who sees in Jenny vast potential to break out of the usual social straitjacket for young women; and Emma Thompson in a three-scene cameo as a headmistress who's all about social straitjackets, the tighter the better.

“;An Education”; is directed by a Danish woman, Lone Scherfig, whose command of mid-century British social considerations is extraordinary, down to the body English of all involved.

But the film belongs to Carey Mulligan. At one point, Jenny allows the Rosamund Pike character to indulge her in party dress-up, and the result is an alarmingly similar female icon of that era, Audrey Hepburn.

Jenny suddenly looks sophisticated, but we know, from the arc of life experience, that looks are deceiving.