BREAKING AWAY -- AMC Academy 6, Belair, Fair City, Hybla Valley, K-B Baronet West, K-B Janus and Town Center.

He's an American kid with nothing special to do, so naturally he gets into differences with his parents about hair, music, and family relationships. But because "Breaking Away" is a film with a happy and intelligent imagination, crediting the American teenager with more inventiveness than a more mean-spirited popular culture would admit, these conflicts have a charming originality.

Hair -- the boy shocks his parents by shaving his legs, having read that Italian bicycle racers do that to cut down wind resistance.

Music -- he has his phonograph blasting opera through the house all the time and, what's more, he hums and sings snatches of Italian opera, and serenades a girl with them.

Family -- He hugs his parents, respectfully calls them Mamman and Papa, and urges them to have another baby.

This particular blond Midwestern teenager has, in sum, decided to become a Neapolitan teenager. Right in the middle of Bloomington, Indiana.

It serves almost as well as the standard provacations to make parents roll their eyes heavenward and announce they can't take it any longer. But these are no matters to tear family life or the society apart. They are the awkward, grand, playful and ingenious snobberies of youth experimenting with shaping life.

Indiana, after all, is Booth Tarkington country, where Penrod anticipated Sam Spade, Alic Adams played an early Bianca Jagger with her chic walking stick, and William Sylvanus Baxter "was seventeen long years of age, and had learned to present the appearance of one who possesses inside information about life and knows all strangers and most acquaintances to be of inferior caste, costume and intelligence."

Peter Yates' "Breaking Away" is in that tradition of toughing and funny stories of growing up. For those who complain that there are no good family movies any more, here's one -- rated PG. In this case, it's not just a matter of being suitable for everyone, which iis a euphemism now for the negatiive virtue of lacking explicit sex scenes, but pertinent to two generations.

The story tradition is episodic, rather than tightly plotted. In "Breaking Away," the ersatz Italian, whom Dennis Christopher plays with freshness and humor, is a town kids who, with hiis pals, lives in a suspended state somewhere between high school and life.

They are townies, derisively called "cutters" by supercilious University of Indiana students, as many of the local kids' parents were or are stone-cutters in the nearby quarries. The town-gown conflict comes to an improbable but nonetheless exciting climax with a decisive bicycle race. But like the hero's differences with his mother and father, played with delightful patience by Barbara Barrie and equally delightful impatience by Paul Dooley, this split is not fatal. At the end, there's no excuse for the boy's staying out of the university, which does not require him to surrender his originality.

He has only had to grow up one more step. CAPTION: Picture, DENNIS CHRISTOPHER DRIVING PAUL DOOLEY, AS HIS FATHER, CRAZY BY PRETENDING TO BE ITALIAN.