THERE'S A GREAT MOVIE bursting to come out of Teaching Mrs. Tingle. Unfortunately, Kevin Williamson's directorial debut lacks the courage of its convictions, and fails to live up to its full potential (rather like Mrs. Tingle's students). What makes this all the more frustrating is that the glimpses of what the film might have been are surprisingly tantalizing.

Amid the slew of teen flicks swamping the multiplexes, Williamson's are among the few that tap the zeitgeist of American youth. Indeed, Williamson can be credited (or held responsible) for the recent eruption of teen-themed fare, due to the success of the hip slasher pic Scream, for which he wrote the screenplay. The inevitable sequel followed, but Williamson was smart enough to send up his own creation; the film-within-a-film twist has Scream 2's characters forced to relive the murder spree in Scream when the events are used as the basis for a film jokingly called Stab. Williamson has since moved to television, creating the teenage drama series Dawson's Creek.

Teaching Mrs. Tingle was actually Williamson's first screenplay, and the success of his later work enabled him to finally bring it to the screen, with himself as director. And so we're back in high-school-land again, among those all-too-familiar stock characters: "nice girl" Leigh Ann (Dawson Creek's Katie Holmes); "fast girl" Jo Lynn (Marisa Coughlan); and "bad boy" Luke (Barry Watson). Leigh Ann, an aspiring writer, is hoping to escape the drudgery of small-town life, but her only ticket out is a college scholarship. As number two in her class, she's in the running; all she needs is one more "A" to close the deal.

Enter Mrs. Tingle (Helen Mirren). As Grandsboro High's history teacher, she's feared by staff and students alike. People scatter as she strides down the hall, and her withering look is matched only by her sarcasm. Through a blunder on Luke's part, Mrs. Tingle comes to suspect that the three friends plan to cheat on their final exam. When the three confront Tingle at her home, the situation spirals out of control, and Tingle ends up tied to her bed, a hostage in her own house.

Anyone familiar with Mirren's work won't be surprised that she steals the film. This is partly because villains traditionally get the best lines, but Mirren's skill really comes through because of the physical limitations of the role -- her character is immobile for over half the film. Even tied up, Tingle presents a threat, for her clear-eyed assessment of other people allows her to subtly manipulate her captors. The kids might be in charge, but Tingle's still calling the shots.

People in this country are probably most familiar with Mirren's work as Detective Chief Inspector Jane Tennison in the groundbreaking British TV series Prime Suspect (shown here on PBS). Mirren's Tennison is tough, and a fighter -- a woman whose dedication to her job inevitably implodes her personal relationships. Some of Tennison's steely determination can be seen in Mirren's portrayal of Eve Tingle, even in her tight, brisk walk down the corridor (also bringing to mind the intensity we saw in Hillary Clinton during the first few years of President Clinton's administration). Tingle could even represent what Tennison might have become, had the detective not had the safety valve of crime work to unleash her personal frustrations.

But if Tingle is ultimately shown as being wracked with bitterness, she's still great fun to watch. Mirren imbues the delivery of words like "SCAN-dal" with a wicked charm, her eyes sparkling as she runs psychological rings around her hapless students. She becomes the kind of clever adversary you end up rooting for, à la Linda Fiorentino's star turn as the scheming Bridget in The Last Seduction.

The personalities of the high schoolers can't compare. Coughlan comes off the best, affecting a sophistication that quickly collapses under pressure. Holmes is sweet, and that's all she's required to be. And though the film makes much of Leigh Ann's inability to snag a guy 'cause she's minus a father figure, isn't it more likely that she's not interested in Luke because he's such a dolt?

For an all-too-brief moment, it looks like the film might end on an irresistibly black note. Instead, Williamson serves up the kind of safe ending you choose if you haven't the nerve to go for broke (even the film's original title, Killing Mrs. Tingle, was reportedly scrapped in the wake of the Columbine killings). It's a pity. How wonderful it would have been to see Mrs. Tingle deliver the coup de grace.