THE LAST THING today's acheivement-oriented, disco cool generation wants to see is a movie vaunting sixties nostalgia. Flower Child Groovies, Peace On Earth, and Power to the People are ridiculed slogans. Can anyone take Jerry Rubin seriously when in 1979 he summons BU students to sit-ins and protest rallies, regardless of cause?

When Hair the play opened in Los Angeles about 11 years ago, the Aquarius theatre's exterior wall faced the parking lot muraled in a spiralling Beardsley-style medley of psychedelic colors and stereotyped figures on their way to Woodstock. That was when we were in the midst of Vietnam, Chicago 7, Timothy Leary and Hare Krishna. The play poked fun at everyone, including its own heroes to some degree, but some earnest zeal and anger permeated, betraying a sympathy with the movement. Fortunately, the movie is handled with humor and a light easygoing attitude which circumvents the cringing prospect of being subjected to cliched pseudo-ideologies. It's a celebration of sorts; catchy, familiar music with some very funny lyrics accompanied by superb choreography. It has an immensely appealing fantasy-like quality which almost makes you want to jump and join in on the fun.

Claude, played by John Savage, awkwardly parts from his red-necked dad as the movie opens. The Greyhound approaches a foggy Oklahoma road, taking Claude to New York City where he is to spend his last days of liberty before enlisting into the Armed Forces. At Central Park, Claude meets up with his soon-to-be buddies who triumphantly ask him to spare some change. Amused by their long hair and "I've Got Life' spirit, he finally reaches into his pocket.

In return, they let him know where they're at through the first dance sequence, Aquarius. The number, like all the rest, is infectuously buoyant. The camera unerringly swoons and follows the gliding choreography by Twyla Tharp: the film's greatest asset. Avoiding cute, stagey, Broadway production-type dance, Twyla Tharp has given new hope to musical choreography. The movements flow naturally; instead of watching a static dance number, we are taken by the camera into the movements, intrinsically swaying with them.

Milos Foreman, the Czech director, makes it all very lighthearted and a bit absurd. There is a fantastic equestrian dance sequence in the Aquarius number where two mounted police stallions do a perfectly synchronized two-step.

The key to this absurdity is the well balanced slapstick and caricatured roles. The establishment is represented by truly Establishment figures clad in uptight strait-laced uniforms of preppie pink satin and navy pin stripe, a glossy Chivas Regal wealth versus patched jeans-adolescent revolt. It's fun to watch Treat Williams traipsing across an elaborately laid banquet table, trying to maximize shattered crystal in his path. It's not to be taken seriously, and thereby doesn't offend our sophisticated Seventies cynicism.

As part of Claude's re-education, how can we overlook the essential acid trip? It's administered to him eucharistically by Treat Williams, demagogue of our clan. John Savage does amazing things with his face, acquiring a glassy-eyed glazed expression as his mind launches through fabricated fantasies of wedded bliss with the luscious Beverly D'Angelo (former debutante gone bourgeois freak) to fantasies of back home in the mid-west American Gothic nightmare. These are tangents which are intelligent, tightly edited and don't resort to multi-layered montage fade outs. John Savage does a convincing portraval of the pleasantly naive Oakie, true to his silent American upbringing. (Unbelievably, he was shooting at the same time for The Deerhunter, in Thailand).

This isn't to say that the film is unflawed. There are moments when the film gets carried away with itself. In "How Can People Be So Cruel," mother and angelic, teary eyed three-year old too-loudly protest to the breadwinning hulk who has left them for hedonistic diversion with the mindless Annie Golden, pregnant with yet another teary eyed mulatto. Annie advises the abandoned mother not to be so uptight, we all love each other, it's cool...But even these gushing scenes are appropriate to the rhythm of levity and humor, and don't really deserve scathing criticism.

An American director might have struggled more self-consciously with the concept of a filmed Hair, unearthing the despair and shame, the horror and uncertainties of the late sixties. But Hair is too light a vehicle for that kind of agonizing exorcism it would have been mawkish, shallow posturing. Someday an American director will film that scraggly mess. But for now, Milos Foreman keeps Hair cheerfully scruffy.