Prom and circumstance: American rite of Spring

It is spring. You can tell because the flowering trees are in full and glorious blossom. You can tell because the bright-colored songbirds have returned. And you can tell because the high school seniors, abandoning casual dress and informal demeanor, are decking themselves out for one of America's great anachronisms: the annual high school prom.

For if spring is a time of color and song, it is also the season for the prom - the grand formal dance with which, by longstanding tradition, the school year ends. After falling out of favor in the '60s, the prom is now back in fashion. But if it is fashYonable, it is clearly not haute couture. It is no cotillion, no social whirl reserved only for debutantes. It is typically organized by the junior class and given as a triumphal gift to those about to graduate. Far from being exclusive, it is a come-one, come-all affair.

For America, after all, is a democracy. It has a publicly funded school system that, for all its faults, still captures the bulk of the teen-age population. To be sure, it has its tiny minority who have already come onto speaking terms with suspenders and French cuffs, with crinolines and lace. But fop the bulk of the seniors - the sons and daughters of the professional and workaday world - the prom may well be the first time such finery has been seen, let alone experienced.

The American teen-ager, after all, is a species whose typical late-spring plumage includes T-shirts, overalls, and cut-off blue jeans. To ''dress up,'' in ordinary language, is to don sweaters, slacks, and skirts. Yet for one brief evening in late May or early June (with seniors, as with birds, the season varies according to precise location), all that changes. Everywhere, from Florida to Oregon, young men trim their hard-won beards, rent the fanciest of formal wear, and vacuum out the family car. Everywhere, from tiny regional high schools on the Great Plains to the vast institutions of the metropolitian suburbs, young ladies perm their carefully cultivated hair, choose their best jewelry, and zip themselves into crinkling evening gowns. Everywhere, the careless Yankee ease gives way to a stiff and studied elegance. Everywhere, formality descends.

Yet if the distance between the frayed running shoe and the patent-leather Oxford is staggering, even more so is the distance between the typical Saturday night party and the Night of the Prom. By tradition, the prom is usually held at the school. In many ways, of course, that is convenient: The seniors all know where to find it, there is ample parking, and the chaperons know the environment. But it also has a mighty drawback. Most schools do not have ballrooms.

And therein lies the great alchemy of the prom: the effort to transform a high-ceilinged, slightly malodorous, and entirely utilitarian gymnasium into a gala dance floor. Not only does it take the cooperation of the entire athletic department, whose coaches make it their duty to worry about the effect of nonrubber soles on their polished hardwood floors. Not only does it take yards of crepe paper, dozens of Chinese lanterns, and the loan of as many potted trees as can be had. It also takes astonishing imagination. The measure of the genius of the decoration committee, in fact, rests in one single point: how successfully they can cover up the basketball backboards and nets that are a universal feature of gymnasiums.

Somehow it all comes together, though, and by dinnertime on the chosen Saturday the quasi-ballroom stands ready. The musicians begin to assemble on the low stage - made of heavy plywood risers lugged in by the custodians from the auditorium, where they usually support the back rows of the school chorus, and now covered with carpet and frilled paper. Even in the music, however, formality takes its toll: A generation accustomed to quadraphonic sound, overdubbing, and all the wizardry of electronic sound has to settle for live music. If the music committee has done its proper work, in fact, the band will be slightly old-fashioned. Somewhere among the guitars and electric pianos one might find a trumpet or a saxophone. Hidden in its repertoire, there may even be a waltz.

But let us leave the drummer, tightening the wing nut atop his last cymbal and giving the wood-block a preliminary tap. For even as he does so, his audience is beginning to assemble itself elsewhere. Out of dozens of doorways all over town step dozens of young men - serious, decorous, and acutely aware of their tails and cuff links. Into dozens of well-scrubbed family cars they step, carrying cardboard corsage boxes fragrant with gardenias. The ringing of doorbells sends dozens of young ladies upstairs in last-minute flurries - and provokes, from dozens of younger sisters and brothers waiting below, titters of laughter from behind half-opened doors. They are watching what may be the evening's most awkward moment: dozens of ill-at-ease young men, sitting bravely in living rooms with mothers, fathers, aunts, uncles, grandparents, and neighbors, waiting what seems like an eternity for the dozens of young ladies to descend the stairs in all their finery. Once together, the honored couple laughs and jokes at their own fanciness: They have no language, no social custom, with which to treat it seriously. They blush slightly as, posed for pictures before the fireplace, he pins on her corsage to murmurs of familial approval.

And then they are off - not yet to the dance, but to dinner. For it is de rigueur that such an occasion be preceded by a dinner of corresponding pomp. The typical prom dinner is a matter of two or three couples arranging to meet together for whatever is best among the local restaurants. And as there are always (except in the large cities) far more seniors than there are restaurants, small flocks of them happen upon one another in the presence of the maitre d' - and cannot avoid the comments of the other diners, who turn back to one another after they have passed to murmur, ''Aren't they just beautiful!''

And so they are, not only of feather but of attitude. For the clothes, in their subtle way, shape the consciousness that wears them. To the young men, who have worked evenings at the grocery store or weekends at the car wash to save for this night, it is a time of conspicuous generosity. Over them comes that sense of grandeur - partly the freedom of maturity, partly the devil-may-care urge of luxury - that leads them to order the next-to-the-most-expensive item on the menu. To the young ladies, it is a time of anxious and considerate graciousness. They are careful to overlook the lobster and chateaubriand. But they firmly avoid the lower end of the spectrum as well, where modest cost might insult the well-prepared charity of their escorts.

And so to the dance itself: candles lit on tables around the edges, the band playing more quietly than expected, the colored spotlights glowing softly. From the center of the ceiling hangs the ubiquitous sphere, bobbing like a weather balloon covered with tiny mirrors. As it twirls slowly, it shreds the blues and reds and greens of the spotlights into a thousand slivers of light, sparkling across the walls, the dance floor, and the faces and clothes of the dancers moving below. Under such novel light, the dancers are not exactly stiff, nor precisely awkward. Yet they exude a self-conscious wonder. This is, as they well know, only the gym. Yet somehow it is more than that. Over there are only Rick and Carol, Jim and Midge. Yet somehow they, too, are more than that. They move like timid royalty, embarrassed by newly discovered reserves of charm and grace. They are not quite themselves. Yet, without knowing it, they are on the way toward the selves they will become.

And that is the great value of the prom. For it stands as a kind of bridge between the plains of youth and the high ground of responsibility. It cannot, of course, wreak its magic on the unwilling. It cannot of itself suddenly freshen the grammar nor remove chewing gum. But at least it starts a process. Like the alchemy of the gymnasium, it begins with what is familiar, casual, and utilitarian. And somehow, to some small degree, it transmutes them into the grand, the dazzling, and the rare. It will never make America a nation of diplomats; it will never settle upon the high schools of the land an afflatus of courtly decorum or noblesse oblige. Yet it persists, a kind of inner calling like the migratory impulse of the birds.

This may be an informal nation. But somewhere inside every American, perhaps , is a top-hat-and-tiara mentality, just awaiting the properly engraved invitation.