You may wish you'd never see another movie with teen-agers sneaking into the girls' dorm to the tune of "Treat Me Nice," but Hollywood doesn't feel that way. It's the largest cottage industry in La-la land, for reasons that are, as usual, mostly economic. The audience "skews young"; teen movies have big opening weekends, when the studio's percentage of the take is largest; they can be made on the cheap (no star salaries, no special effects); and young people respond to a catchy ad, which costs less than making a good picture.

Making money from teen movies is, well, as easy as taking candy from a child, or so the wisdom went until last month. The winners were "Witness," an "adult" movie, and the long-running "Beverly Hills Cop," a movie with broad appeal. Among the losers were "Vision Quest," "Turk 182!" "Mischief," "Heaven Help Us," "Fast Forward," "Tuff Turf" and "Heavenly Bodies," all teen movies, and bombs all. Only two among the recent gusher of teen movies, "The Breakfast Club" and "The Sure Thing," promise a modest success. And they're the ones that treat kids like adults.

The pattern is promising, because it suggests the banishment of the marketing geniuses from the field -- making money from the movies, it seems, is as simple and as difficult as making good movies. And when the question is parsed that way -- without the mumbo-jumbo of demographics -- it raises an entirely new question with regard to teen movies: What are kids really like? And why would anyone want to make movies about them?

Start with what kids aren't like, which is simple -- they aren't like kids in these movies. The traditional teen movie is a structural anthropologist's dream. Begin with a group of young men joined by some institution (high school, fraternity, police academy, the Army). Within the first half hour, introduce the celebrated "peeper scene," as simple as climbing a ladder and watching girls undress ("Private School") or as complex as hooking up video cameras and watching girls undress ("Revenge of the Nerds"). At the same time, introduce the antagonists (rich kids, the school administration, parents) who want to bridle the kids' madcap spontaneity. And among the kids, find two heroes: a stud and a nice, confused kid who is the "fill-in-the-blank" for each kid in the audience.

The plot then spins out in routine fashion. More peeper scenes; drink, drugs, and "partying"; the authorities riotously upstaged; the stud's sexual triumphs revealed as hollow; the nice, confused boy finding love with a nice, confused girl. Add thumping rock 'n' roll (to augment theatrical box office with album sales), conclude with the hero narrating a "where are they now?" epilogue, and there you have it -- echt teen sex comedy.

Nobody thinks of his own movie this way. Noel Black saw his "Mischief" as an homage to his midwestern boyhood; Charles Purpura wrote "Heaven Help Us" to evoke his own formative years in parochial school in Brooklyn. If the studios are cynical, the screenwriters are sincere. For them, the attraction of the genre lies in returning to an innocent time, where everything is new, vibrating with the freshness of discovery. Sex is familiar to these filmmakers, now in their thirties, and love's a canard; they fondly recall that time when girls were vessels of mystery, love something you naturally believed in, when even your own body, wracked by puberty, was something new and strange.

The idea of celebrating innocence through movies so hermetically formulaic is, of course, preposterous; the teen movies exalt spontaneity while they squeeze every drop of it from the frame. Much of this is the studios' fault. When a genuinely personal screenplay about somebody's teen years comes in, it's farmed out to "professionals" who add the de rigueur elements. This, apparently, is what happened to "Heaven Help Us," a movie that seems to have started out being about a certain kind of boyhood and ended up being about Everyboyhood.

But the plastic flavor of these movies fits, in a way, because they're founded on a deception. While the message is moralistic (love is more important than sex), that message is denied by the images. The brio of the genre is devoted to the peeper scenes; the camera lingers, not on dewy eyes, but on breasts. You remember the toga party from "Animal House," not the "tender" romance between Peter Riegert and Karen Allen.

There's a neurosis at work in the teen sex genre -- it's a species of revisionist history. The vision is of the filmmaker, driving a Porsche, returning to his old high school and scoring with girls who (as part of the revisionism) are suddenly all beautiful. Virginity is valuable as something to be defiled. Lurking beneath the surface is a screenwriter who is the archetypal dirty old man.

As a genre, these movies are relative newcomers. In the old days, when they made movies about kids -- the Dead End Kids, Shirley Temple, Mickey Rooney -- they weren't for kids. The youngster toting a dime to the Bijou is familiar enough in our mythology, but the movies he saw were "pictures for the whole family." Roger Corman was the first to aim specifically at the teen audience; the horror and exploitation movies he made in the '50s were tailored for boys and girls going to the drive-in on Friday night. But the Corman pictures, like the Frankie Avalon-Annette Funicello movies of the '60s, existed on the fringes of the movie business -- they were distributed by Sam Arkoff's American International Pictures, not the major studios.

Teen movies as we know them today started in 1973 with George Lucas' "American Graffiti," which came out of nowhere to make tons of dough and cop an Oscar nomination. That opened a lot of eyes in Hollywood. The genre was refined by "Animal House," which added the gross-out element, and "Porky's," which added soft-core porn. The rest, as they say, is history.

The art of "American Graffiti" provides a useful comparison with the artifice of the genre today. "Fast Forward" gives us good suburban kids and bad lower-class inner-city kids; "Mischief" and "Heavenly Bodies" give us the usual evil richies; "Tuff Turf" flips that -- the hero is a rich kid, his adversary a poor tough Latino -- but the class assumptions remain black-and-white. "American Graffiti," on the other hand, layers and nuances the juxtaposition by shifting the point of view. From Richard Dreyfuss' vantage, the "greasers" are admirably raffish, and his inclusion among them, on the night before he goes off to college, caps his high school career; he prizes his friendship with the king of the hot rods (Paul Le Mat). But they're also pathetic -- Dreyfuss knows that (with his quirky integrity, he likes being with them, but doesn't want to be of them), and so does Le Mat. He approaches this last night with a brooding sense of doom, knowing that once high school is done, he'll be just another gas station attendant.

While the sense of loss in contemporary teen movies is banal and dirty (in "Mischief," it's simply the lost opportunity of sleeping with virgins), the sense of that permeates Lucas' movie is expressed in haunting images of loneliness (Wolfman Jack, small and solitary in his broadcasting booth) and distant romance (Suzanne Somers' T-Bird diminishing on the highway as Dreyfuss' plane lifts off toward the East Coast). "American Graffiti" started the mania for period sound tracks ("Heaven Help Us" compulsively plays hits from the era, as if the billboard "BROOKLYN 1963" weren't enough); but in "Graffiti," the music is thematic as well -- the sound track is tinny, hollow, as if it's decaying into memory even as it plays.

The bones of "American Graffiti" have been thoroughly picked (Terry the Toad, added to the margins of "American Graffiti" to provide comic relief, became a whole movie -- "Revenge of the Nerds"). What's lost is Lucas' depth of emotion, his respect for his characters. The form remains, but the feeling is gone.

"The Sure Thing" and "The Breakfast Club" explicitly set themselves against the teen sex genre -- there is no nudity, no peeper scene, no "gross-out." They are "tender" and "serious," and have been celebrated by several critics for that. They also have nothing to do with real kids.

For the new cliche's of the teen sex genre, these movies substitute the old cliche's of old movies. "The Sure Thing" gives us kids acting like adults in a '30s romance -- they're Clark Gable and Claudette Colbert from "It Happened One Night" in miniature; the kids in "The Breakfast Club," babbling confessions at each other, are refugees from a '50s psychodrama like "Twelve Angry Men." This is supposed to be "refreshing."

But everything about Rob Reiner's "The Sure Thing" is phony. The essence of the hero's character is that he's tired of sex (he'll take romance), which is a peculiar complaint for someone who's a virgin -- it's more the feeling of someone in his late twenties who wants to get off the singles bar roller-coaster (like "Splash" 's Tom Hanks). He's devil-may-care; his beloved, on the other hand, is prematurely old, a chronic disapprover. What brings these kids together? Love! But love, in "The Sure Thing," doesn't grow out of character -- it's a plot solution superimposed from above.

The kids of "The Breakfast Club" are so terrified by their teen-age identity crises, they grab hold of the first persona that offers itself -- they become a "brain," a "jock," and so forth. But unlike John Sayles' "Baby, It's You," which subsumed the problem of identity to the more basic problem of telling a story, "The Breakfast Club" wears its themes on its sleeve. And where Sayles never blinked from the desperation involved in the search for identity, writer/director John Hughes comes up with a solution as ersatz as Reiner's. When the kids finally "find themselves," they find a generic identity -- they define themselves by their enemies (adults in general). They're simply "nonadults." The kids of "The Breakfast Club" solve their identity crises by deciding to have no identity at all.

For all their pretensions, "The Sure Thing" and "The Breakfast Club" just repeat the themes of the teen sex genre. "The Sure Thing" exalts love over sex (worse, sex here is made a straw man); "The Breakfast Club," rife with stale class assumptions, shows us kids triumphing over authority, with the unremarkable exception that the victory is "psychological." The message of the teen sex movies is that kids are all the same -- in "Porky's," everyone's a slathering agent of id -- and that's the message of these movies, too.

In "The Sure Thing," opposites attract because the things that make them opposites don't mean anything -- they're united by some vague, all-purpose love. And in "The Breakfast Club," the kids are united by their essential kidness. It's just a higher form of the same condescension.

"We all end up as packaged goods," Westbrook Pegler once remarked; we apotheosize the teen years because that's the time when we're not packaged goods, when we're possessed by vistas, filled with the romance of endless possibility, and terrified by it. In our teen years, we design at least the outlines of the person we want to be -- no other time in life is so volatile. And at the same time we are introduced to those hormones that soon establish their durable tyranny.

The problem with teen movies is that they see these forces as discrete, as if two different people decided the questions of who they wanted to be, and how to deal with sex. The great virtue of Maurice Pialat's "A Nos Amours" is that it sees them as seamless, indivisible. "A Nos Amours" follows a 16-year-old girl through a number of relationships with men, none of which equals the intensity of her relationship with her father who, early in the movie, divorces her mother.

Sex informs identity (she becomes a seductress); identity informs sex -- her sexual alienation is the product of her family life. The girl's mother loathes her sexuality, which has saddled her with an unhappy marriage and progeny she hates; that loathing is translated, in the girl, into distant promiscuity. "A Nos Amours" punctures the romance at the heart of teen movies -- there are no "endless possibilities," there are no possibilities at all. In Pialat's universe, we are prisoners of sex because we are prisoners of who we are.

What "A Nos Amours" reveals is that the things that are interesting about kids become even more interesting in adult life; the things you become aware of as a teen-ager (the relations between self, sex and family) deepen into a complex latticework when you get older, in the same way that skin ages. The actual themes of a teen-ager's life don't leave him when he grow up -- they just deepen; but in teen-hood, they're brighter and more obvious to the eye. "A Nos Amours" does what the best teen movies do -- it's the book of life, brightened by a student's magic marker.