There’s been a lot of time-travelling in movies lately; here’s one that tries to transport the viewers, rather than the characters, back to the teen comedies of the eighties and nineties. “The Duff” resurrects the old formula in which the outcast girl is wooed by a handsome guy for some reason (maybe a bet, maybe he’s been hired, maybe he needs her help in class, etc.) and they wind up—surprise, surprise!—together. It tries to give that hoary chestnut an updating by tossing in social media as an ingredient, but ironically that only accentuates the creakiness of the plot. The result is a tepid, undernourished clone of the John Hughes high school template, with attractive leads stuck in a script that feels like a tattered hand-me-down.

Ingratiating Mae Whitman stars as Bianca Piper, a spunky, intelligent high school student who’s part of a threesome with long-time friends Jess (Skyler Samuels) and Casey (Bianca Santos), though those two are more conventionally attractive than she is. She thinks nothing of the differences among them, however, until her hated next-door neighbor Wesley (Robbie Amell), a handsome hunk who’s the school’s quarterback in an off-and-on relationship with campus mean girl Madison (Bella Thorne), points out nonchalantly that she’s the DUFF of the group—the “designated ugly fat friend” who serves to help the others in a variety of ways, though without realizing the role she (or he) is filling. The recognition that he’s right enrages her, causing her to break off contact (via social media as well as in person) with her erstwhile pals.

But that’s not the end of things. Anxious to change her image in order to attract Toby Tucker (Nick Eversman), the pretty boy she’s long been infatuated with, she enlists Wesley, who’s facing being kicked off the football squad because of his grades and desperately needs her help, to give her a makeover. That infuriates Madison, who thinks Bianca’s poaching on her turf and uses footage of an embarrassing mall outing between Bianca and Wesley taken by her lackey Caitlyn (Rebecca Weil) to embarrass her presumed rival online. The incident doesn’t deter Bianca from continuing her pursuit of Toby, however, though you’ll get no prize for correctly predicting whom she’ll finally wind up locking lips with, even after Mr. Tucker invites her over to his place for dinner.

Whitman throws herself totally into “The DUFF,” engaging in lots of slapstick sequences (that mall trying-on-clothes sequence, another at Toby’s house) that seem ready-made for a young Lucille Ball. (Nonetheless she’s not, it must be pointed out, terribly convincing as a frumpy type.) Amill, who’s liberated from the comic-book seriousness of his television roles on “The Tomorrow People” and “The Flash,” smiles a lot, even though there are dark clouds in Wesley’s home life., and overall cuts a likable figure. The rest of the young actors are stuck in stock parts and play them that way—Weil is used especially poorly, since Caitlyn isn’t even a stereotype, merely a plot device to get stuff photographed on her omnipresent smartphone (she appears to be everywhere by simple happenstance), though Thorne is probably the most irritating of them.

A few adults are thrown into the mix, though most of them act more childishly than the students. Allison Janney has the thankless duty of playing Bianca’s mother, who’s responded to her divorce by becoming a motivational speaker slash author—a sitcom contrivance if ever there was one. Romany Malco, as the school principal, and Ken Jeong, as the campus newspaper advisor who forces Bianca to write about the homecoming dance (an occasion which, like the prom, inevitably provides the setting for such a movie’s conclusion)—along with Chris Wylde, as the chemistry teacher—mug uncontrollably, the last two especially in the blooper clips cut into the end credits. It helps none of the actors that neophyte feature helmer Ari Sandel paces everything sluggishly, and the editing (credited to Wendy Greene and Bricmont) lets scenes run on too long; the movie could easily have been trimmed by twenty minutes without much loss. On the other hand, the physical production is above average, with David Hennings’ widescreen cinematography rather attractive.

In the end, though, “The DUFF” represents another failed attempt to recapture the magic of Hughes’ high school pictures. And, of course, the moral it preaches at the close isn’t exactly in synch with the action. Bianca, in a rewrite of her article, instructs her readers that you don’t have to be popular and with the guy of your dreams to be happy. But that’s after she’s gone through a makeover as complete as the one Ally Sheedy endured in “The Breakfast Club” or Rachael Leigh Cook in “She’s All That,” is being feted by her classmates and is waltzing off with—well, you know. She’s beautiful, popular and on the arm of the guy her dreams—which, one supposes, is the high school version of “Do as I say, not as I do.”