“Irremediably sappy” is far too benign a description for this teen tearjerker, which shamelessly embraces every possible cliche in a desperate effort to wring laughs and sobs out of a seemingly impossible high school romance. Despite its hopeful title (which clumsily conflates “An Affair to Remember” with “A Walk in the Clouds”), this preposterously cornball little movie–basically an elongated version of a sappy afterschool TV special–wouldn’t stay in the memory at all, except for the fact that it crams so much hackneyed material within the compass of a mere hundred minutes. The result is pretty gruesome, a supremely schmaltzy sudser that manages to be both laughably predictable and absurdly pious.

The narrative is based on that old standby, the “unlikely attraction” between two very different kids. Landon (Shane West) is a popular guy who’s part of the gang that gets its jollies from humiliating straight-arrow types desirous of joining their number. When one of the group’s pranks goes wrong, Landon shows there’s something good underneath his flippant exterior by rescuing their victim and getting caught as a result. He’s soon assigned a variety of unpalatable tasks as penance, including a requirement to participate in school’s spring musical; and to help him learn his lines he seeks out the aid of do-gooder Jamie (Mandy Moore), the plain-Jane daughter of Reverend Sullivan (Peter Coyote), who also happens to have a spectacular voice and will star in the show. It comes as a shock to everybody else in the movie–but to nobody in the audience–that the two inch toward love, a circumstance that puzzles Landon’s buddies (and angers his old girlfriend) while frightening Jamie’s father. Landon, of course, is torn between his old life and his new affection as his feelings for Jamie grow ever stronger. But, alas, their unhindered happiness is not to be. A big revelation occurs about two-thirds of the way in to divert the course of true love, but given the character of the piece, it will surprise nobody up on his Erich Segal. The twist turns this “Walk” into an ramble in Fannie Hurst territory. The denouement is designed to be both weepy and uplifting, but fails on both counts.

Perhaps if this material had been played for laughs, it might have had a chance, but Adam Shankman treats it as earnest melodrama, which proves the kiss of death. (Of course, Shankman proved inept with the farce of “The Wedding Planner” too, so he probably couldn’t have pulled it off in a lighter vein either.) Nor are the leads charismatic enough to win us over. West gives Landon the old high school try, but he seems a generic teen, and his acting is dogged but uninspired. (“Are you trying to be bad at this?” the drama teacher inquires of Landon/West at the first reading. To which he replies–only half-jokingly, as it turns out–“No, it comes naturally.”) The only thing remarkable about him is that physically he rather resembles the middle brother in a family including Neil Patrick Harris (“Doogie Howser”) and Christopher Masterson (“Malcolm in the Middle”). As for Moore, the singer who plays upright Jamie, she’d be well advised not to quit her day job. While she doesn’t come off quite as badly as Mariah Carey did in “Glitter,” she’s not appreciably better, either. (It doesn’t help that her character’s transformation from old- maidish geek to sultry femme fatale in the school musical is laughably abrupt.) Coyote looks understandably crestfallen in the role of the preacher-father, a part which remains as hopeless as it was when John Lithgow sank doing it in 1984’s “Footloose.” (It’s also odd to find that this hell-fire Protestant minister bears the unlikely name of Sullivan.) Daryl Hannah shows up with dark hair to play Landon’s understanding mother; you have to give her credit for taking on a role like this, but she doesn’t do much with it. The young players in supporting parts are generally badly directed, but in any event they’re stuck in stereotypical roles (the rebel-without-a-cause, complete with hot-rod; the sulky, vengeful girlfriend, who embarrasses shy Jamie; the obligatory African-American cutup who dances well) that wouldn’t be out of place in “Not Another Teen Movie.”

At one point in the narrative, Landon explains his agnosticism to Jamie with the remark, “There’s too much bad s–t in this world.” To which the viewer of this malodorous effort can only say, in the pious tones the movie itself encourages, “Amen.” “A Walk to Remember” is a movie to forget.