After-school television special rises above classroom clich'es

``I JUST saw the latest test results from your class. What exactly are you doing right?'' The question - asked of a teacher on tomorrow's ``ABC Afterschool Specials'' program - may echo a well-worn story idea, but its main point is richly worth retelling. The teacher being questioned is an appealing maverick named Sam Greene, and what he's doing right is demonstrating once again that enlightened determination can work wonders in a classroom.

Admittedly, ``Class Act: A Teachers Story'' (ABC, Wed., Mar. 18, 4-5 p.m.) is loaded with classroom-movie clich'es: well-intentioned new teacher faces a cynical and disorderly class that forms a cross-section of supposed losers, including a ring leader (Reggie) who snickers, ``How much you want to bet this one won't last?'' and a talented artist who doesn't know where to turn for encouragement. Sam also faces a weary faculty who greet his question, ``Come on, how bad can kids get'' with semi-bitter laughs.

But there's much about the show that's not routine. The character of Sam - who succeeds in turning around the students' belligerently defeatist attitude about school and about themselves - offers young viewers a distinctly non-idealized hero. He's harried by the uncooperative loose ends of his life, both physical and emotional: an ex-wife who leaves coyly badgering taped phone messages about alimony on the answering machine; a rusted-out convertible that gets towed away; a decrepit apartment. This is not a starry-eyed educational crusader, but a credible person whose faith in kids can stand the rigors of real life.

And fortunately, Sam is played by Ron Leibman, who beautifully illustrates just how much new life a strong actor can give an old plot. In Mr. Leibman's hands, Sam becomes a convincing bundle of minor eccentricities and personal quirks. He is so self-deprecating in his reactions, so jaunty and sarcastically affectionate toward his students, that you accept large portions of an otherwise concocted story whose cast of movie misfits seems salvageable right from the start. Reggie's sensitivity and caring, for instance, lie just beneath the brazen stance, ready to surface after some skillful probing by a man he grows to trust - Sam Greene.

The sardonic humor of Leibman's peformance gives Sam the non-sentimentality he needs for viewers to accept his efforts as real, even if the object of his efforts - the students - seem slightly unreal. His unorthodox way of turning the class into winners makes the struggle not only believable but heartening. He forms a soccer team over official resistance, fines students for mouthing off, pays them for thoughtful questions, and uses the class kitty for pizza parties.

We don't really witness their grudging capitulation to his view, but the stress in this ``teacher's story'' is distinctly on the teacher, and that's why so much of it works. Sam's own background and feelings are brought into the battle for the students' futures, which results in the artist's getting a spectacular career break, and other signs of the class's new hold on the future. And Sam's own faith in people - partly dislodged by his past - has been restored by his efforts to get the class to trust him. When he says, ``This is going to be a class act, in spite of yourselves,'' Sam seems to speaking to himself as much as he is to the class, and that's why the audience will believe that this classful of ex-skeptics has been given a hard push into a promising new life.