First movies stopped being like plays; then plays stopped being like group therapy -- characters badgering each other until, emotionally drained in the third act, they bared their souls in melodramatic monologues. But who says you can't recapture the past? Taking place almost entirely in one room, "The Breakfast Club" is the kind of movie -- and the kind of play -- that's hardly seen anymore. And good riddance.

Having misbehaved in various ways, five high school students are slated to spend Saturday in detention together. Two come from the school's elite -- a varsity letterman (Emilio Estevez) and an adolescent socialite (Molly Ringwald). They're joined by two intellectual outcasts -- a math whiz (Anthony Michael Hall) and a kooky artist (Ally Sheedy). The last detainee is a lower-class troublemaker (Judd Nelson).

The troublemaker starts things off with tales of how his father beats him, bullying the other kids with their own privilege -- he has it tough, they don't. As the day drones on, it turns out they all have it tough; they're victims of their parents' and friends' expectations, prisoners of their roles. "The Breakfast Club" begins with a narrated essay, addressed to the school disciplinarian (Paul Gleason), scolding him for seeing them as just "a basket case, a princess, a criminal, a brain and an athlete," when they feel they're human beings, much more complicated than that.

But when the kids finally get down to self-revelation, each states his angst in exactly those terms -- the athlete resents the pressure to win, the brain resents the pressure for grades, and so forth. There's never any sense that, for example, the brain might feel pressure to be an athlete; the confessions seem as forced as the roles they played before. And the adults -- the disciplinarian and the parents, whom we get to know secondhand through the conversation -- are just caricatures. Maybe that's how kids see adults, but writer-director John Hughes has no point of view on the self-deception. It's the kind of undigested vision that might have come from the kids themselves.

As the kids yammer at each other, "The Breakfast Club" becomes as static and uninvolving as most filmed plays; there's none of the ingenious virtuosity that, for example, Robert Altman used in shooting David Rabe's "Streamers." Instead, Hughes tries to break the boredom with rock videos (the kids put records on the library phonograph, and hey, let's dance!), but the stylization of these sequences only underscores the humbug of the whole setup. We go to movies because they allow characters to unfold with the pace of our own lives -- the reality of film is porous, open-ended. Hughes, though, prefers the stagy unities of time (one day) and place (the library). The same things that provide a play with its condensation make the film no more than an exercise.

What's worst about "The Breakfast Club," though, is the way it's structured to provide its stars with opportunities to show off; with one exception, the fine cast indulges itself with actor's turns. In highly orchestrated montages (briskly edited by Dede Allen), one kid will clip a pen on his lip, another will play with the drawstrings of his sweat shirt, another will ignite the sole of his shoe and light his cigarette from it, another will tie a string around her finger till it turns purple. These details aren't woven into the performances to provide characterization; it's just the kind of behavioral display you'd see in an acting class.

Ringwald has an ease before the camera, but her performance is all surface, a more relaxed version of the indulged, pouty brat she gave us in Hughes' "Sixteen Candles." Hall does the same -- he has a weird, jittery comic timing, but when he has to play his Big Scene, the emotionalism comes in a vacuum. Estevez, perhaps the most riveting of the legion of young actors, is merely enervated here; his brooding has none of the wound-up energy he displayed in "Repo Man." Like the rest, he's so busy trying to play the essential kid-ness that draws them together that his performance has a whitewashed, generic blandness. And Nelson, throwing every line to the gallery, roars and postures but never strikes a true note.

Sheedy, on the other hand, gives the performance of her short career. Till now, she's been limited to teen ingenue roles, with mixed success. In "Breakfast Club," she hides behind a mop of hair that looks like a homemade wig, and her loose, soiled sweater and skirt reach to a pair of downtrodden black sneakers; Sheedy doesn't walk, she rolls -- she looks like the Addams Family's Cousin It. She gets at the withdrawn neuroticism of her character without speaking a line -- everything about her is hidden. When the other kids dance, she suddenly collapses in a heap to the ground, a mouse hugging the floor, avoiding the maid's broom. She watches the other kids slyly, silently, teases them without ever letting on that she's teasing -- they're just data for her interior world.

So what does Hughes do with her? Ringwald whips out her eyeliner and gives Sheedy a makeover; with her hair pinned back, she's once again the ordinary teen ingenue, ready to fall in love. For all the slickness of some of the lines, the sometimes acute feel for the rhythms of teen-age speech, "The Breakfast Club" gives us a homogenized sense of what kids are really like -- to wit, that they're all like each other. It's just the old sentimental saw about how, beneath our differences, we're all just, you know, people, except that instead of being phrased in the usual racial or class context, it's carrying a schoolbag.

The Breakfast Club, opening today at area theaters, is rated R; it contains sexual themes and some profanity.