Starring Samuel L. Jackson Directed by Kevin Reynolds Rated R, with profanity and violence Running time 121 minutes We give this film a rating of 5 out of 10

(July 30, 1997) -- Most people who get stabbed in the back -- literally, repeatedly stabbed in the back -- would go out of their way to avoid putting themselves in the same situation again.

Not Brooklyn high school science teacher Trevor Garfield, though. Played with quiet but commanding insight by Samuel L. Jackson, Garfield is a man with a mission -- and the key character in a sobering new film, 187.

He's a man who says the Serenity Prayer, a staple of the Alcoholics Anonymous program, before he goes to work every day, adding his own footnote asking the Lord to help him do what he was "put on this earth to do." He's a man who passionately loves to teach and believes in the redemptive value of education for emotionally deprived urban teens who bring nothing but ignorance and hostility to school every day.

So after he recovers from the wounds inflicted by a Brooklyn high school student who learned he was failing Garfield's science class, the teacher moves to L.A. and takes a substitute job there at a violence-plagued inner-city high school. Drawing its title from the California penal code for homicide and a favorite bit of shorthand among teen gang members, 187 tells the story of this gifted tenacious teacher's gradual but certain voyage to disillusion -- and worse.

First-time screenwriter Scott Yagemann, himself a veteran of seven years' teaching experience in the L.A. public school system, provides final wisdom of the most cheerless kind. Essentially the dramatic arc of his script leads viewers to the conclusion that the sacrifice of sanity and life -- regularly made by teachers in urban schools -- is simply not worth the occasional triumph.

In the film, one Latina from an impoverished illiterate family finds the courage, with Garfield's help, to pursue her dream of becoming a writer. Meanwhile a cluster of dead, dispirited or mutilated students and teachers stand clustered in the wake of her triumph. Garfield urges her to learn the meaning of the phrase "Pyrrhic victory." In the movie's perspective, she not only learns it but also personifies it.

We don't necessarily go to movies to be cheered, and we most particularly don't need any of the kind of false cheer or cynically exploitive yucks dispensed in substandard movies about pressing urban problems. Yet it's impossible to accept the final wisdom Yagemann dispenses in 187 because it is wisdom steeped in despair.

Although the movie's conclusions are unacceptable, director Kevin Reynolds proves an unflinching reporter, one who relies heavily on vivid, authentic detail from the front lines: armed, highly aggressive kids (and armed, very frightened teachers); administrators thrown into inertia by the specter of potentially expensive lawsuits; illiterate, uncaring, helpless or just plain absent parents.

Big-city newspapers record the results of that kind of horror every week, if not every day, but 187 lays it out in the kind of commanding terms that words and still pictures rarely muster.

Beyond high-impact reporting, the movie gains immeasurably from a lead performance that lavishly confirms the virtue of simplicity. Jackson gets strong assistance from John Heard, who in a very few scenes fully communicates the sorrow and the pity of a teacher who has long lived in a perpetual state of panic, and from Clifton Gonzalez Gonzalez, as the macho gang leader who sees Garfield as one more authority figure to cut down.

Yet, finally, this is Jackson's movie. Eyes steady behind his spectacles, voice lowered and modulated, gait slightly stiff to match his veneer, Jackson gives a fastidiously detailed performance that depends on simplicity to suggest the complexity of the character. Under his scholarly, reserved, almost prim exterior is a man whose inner rage has reached the boiling point.

Near film's end, Jackson gets an explosive bit of dialogue: The stabbing was nothing compared to "the robbery," he says. What was stolen? His passion, he explains; his spark, his self-confidence. It's a measure of the performance that you sense the nature of the character's loss, exactly, long before he spells it out.

With Pulp Fiction, A Time to Kill and now 187 to his credit, Jackson has become one of the most formidable actors in U.S. movies, one of the very few leading men who still see themselves as character actors.