''Irt'' Actress Steals Show

XX 1/2 "Just Another Girl on the IRT," with Ariyan Johnson, Kevin Thigpen, Ebony Jerido. Written and directed by Leslie Harris. Broadway Market Cinemas. "R" - Restricted because of frank language, graphic childbirth scene. ----------------------------

Much-ballyhooed as a breakthrough movie for African-American women filmmakers, Leslie Harris' feature-film debut has its startling moments, most of them generated by an attention-getting performance by Ariyan Johnson as a mouthy Brooklyn high-school student named Chantel.

Unfortunately, too much of it ends up playing like an after-school special with four-letter words and lots of screaming. Presented as an honest examination of a savvy student's social and sexual dilemmas, Harris' script ultimately seems evasive and unrealistic, working overtime during its final stretch to deliver an upbeat ending.

Chantel often displays more chutzpah than brains, telling off a frustrated teacher because he wants to discuss the Holocaust, using her boyfriend's cash to go on a shopping spree and self-destructively baiting an uppity yuppie at the Upper West Side gourmet shop where she works.

Harris has acknowledged that she deliberately made Chantel "a little hard to take," in order to get a variety of situations and attitudes into the script. But the character covers such a wide range of behavior that she doesn't always add up.

Still, the talented Johnson brings a sweet brassiness to these

scenes that makes them seem playable in spite of the confusions of the script. She's also vulnerable enough to carry the more dramatic second half, which turns into a kind of horror film about teenage pregnancy.

The best parts of "Just Another Girl on the IRT" deal with the 17-year-old Chantel's panic and denial when she's forced to admit that her options have suddenly been limited by an unwanted child. Her reactions to this state of affairs may be pathetic, even reprehensible when she goes into labor and tries to escape responsibility altogether, but they're always presented with remarkable empathy.

It's almost a one-woman show, although Chantel's best friend and her new boyfriend are well-played, respectively, by Ebony Jerido and Kevin Thigpen. Harris, 32, whose only previous film is a documentary about Planned Parenthood, handles the rest of the cast with assurance.

Shot in just 17 days for about $100,000, "Just Another Girl on the IRT" has an undeniable vitality that helped it win a Sundance Film Festival prize for outstanding achievement in a first feature. It has also drawn flak for a classroom episode that's been widely interpreted as anti-Semitic. However, the scene in question isn't so much offensive as it is underdeveloped.

Intended to demonstrate that Chantel is impatient with history lessons that have nothing to do with contemporary urban problems, it backfires almost completely, suggesting that she simply has no patience with the problems of other minorities.