Grade: C

Stephen Chbosky enjoyed success with his filmization of his own quirky novel, “The Perks of Being a Wallflower.” He stumbles, however, with this follow-up effort, an adaptation of another writer’s book. “Wonder” (not to be confused with Todd Haynes’ marvelous “Wonderstruck”) is a tale of a young boy with a facial disfigurement that tugs at the heartstrings so insistently that you might well leave it feeling assaulted rather than uplifted.

The pint-sized protagonist is Auggie Pullman (Jacob Tremblay), a smart ten-year-old born with a congenital facial deformity that multiple surgeries haven’t entirely resolved. He’s been homeschooled until now by his mother Isabel (Julia Roberts), but she feels it’s now time for him to leave the nest and take classes at a regular school, Beecher Prep, despite the reservations of his loving dad Nate (Owen Wilson). Much of the film centers on the ups and downs he experiences there—the support he’s shown by the headmaster Mr. Tushman (Mandy Patinkin) and teachers Mr. Browne (Daveed Diggs) and Ms. Petosa (Ali Liebert), and the taunts he must endure from bully Julian (Bryce Gheisar) and his band of followers.

Tremblay, the young actor who was so strong in “Room,” makes Auggie a fully sympathetic kid, both at home and in school. You’ll certainly be appalled by the treatment he receives from Julian and his confederates, and happy when he finds a friend in Jack Will (Noah Jupe, who played Matt Damon’s son in the unfortunate “Suburbicon”), whom he helps with science homework and plays video games with. But even in its earliest stages, the bullying business is presented in an overly “afterschool special” sort of way (with Gheisar overdoing his pint-sized Eddie Haskell routine), and by the time Julian’s parents show up for a excuse-making session with Tushman, with Crystal Lowe descending to Cruella de Vil level as his snooty mother, the treatment has descended to the level of sheer caricature.

But the story isn’t simply about Auggie’s eventual embrace by his fellow students—achieved in a rah-rah finale at commencement that couldn’t be more manipulative. It’s also about the people around him—first his genial, gregarious dad and Isabel, who’s put off finishing her master’s thesis while raising her son and now returns to it, her triumph in the end complementing Auggie’s.

And it’s about Jack, whose back story is treated as a conjoined subplot to Auggie’s. He wants to fit in as well, and in trying to do so says something he later realizes he shouldn’t have. It causes a rift with Auggie that threatens not only their friendship but Auggie’s belief that he can trust anyone. Naturally this crisis will be overcome by the end, in a way that seems pretty glib even by tearjerker standards.

Another largely separate chapter focuses on Auggie’s older sister Via (Izabela Vidovic), who has always played second fiddle to her brother (except for her supportive grandma, played in a flashback by Sonia Braga). Her return to school for the new year finds her best friend Miranda (Danielle Rose Russell) much changed, and shunning her for a new crowd. Miranda will get a sub-chapter of her own explaining her change of attitude, but their rift, like Auggie and Jack’s, will be resolved by the close as well, by a decision on Miranda’s part that—to be honest—is meant to be a gesture of ultimate friendship but could easily have become the source of massive humiliation instead. Happily, this subsection of the movie also involves Via finding a sweet, compatible boyfriend (Nadji Jeter) in the process.

As if all this weren’t enough to send the schmaltz meter into overdrive, Chbosky resorts to one of the oldest, moldiest cards in the pack—the canine reaction shot. The Pullmans have an elderly pet, to which the director cuts periodically to elicit another aw! from the audience. Not only that: he takes the cliché to its ultimate point. Precisely what that is won’t be revealed here, but for reference one might want to consult what Wilson has already played out on the screen, in “Marley & Me.” It’s pretty shameless—and all the more so in that it’s utterly gratuitous.

Still, as far as tearjerkers of this kind are concerned, “Wonder” is a class act. Tremblay is as outstanding as he was in “Room,” while Roberts brings her considerable likableness to her role and Wilson’s goofiness is a pleasant complement to it. Jupe is as engaging here as he was in “Suburbicon” (one of the few good things in that clunker); Vidovic, Russell and Jeter makes a good trio; and Patinkin underplays (though, as usual, his underplaying is barely distinguishable from overplaying). The picture is also technically polished, with solid production design (Kalina Ivanov) and cinematography (Don Burgess), though the editing (Mark Livolsi) might have shaved a bit off the nearly two-hour running-time and Marcelo Zarvos’ score could have been more subtle.

Still, if this sort of thing is your cup of tea, “Wonder” is a superior example of it. Just be forewarned that it’s been brewed with lots and lots of sugar.