‘Booksmart’ doesn’t do it by the book — which is just right

Beanie Feldstein and Kaitlyn Dever in “Booksmart.”Annapurna Pictures

“Booksmart” is a delightful entry in a tired genre: the teens-go-wild comedy. Back in the days of “Porky’s,” “Losin’ It,” and “Zapped!,” we used to call these things “stu-coms,” short for “stupid,” and the good ones (“Better Off Dead,” “Risky Business”) were few and far between. Maybe the last decent stu-com was “Superbad,” in 2007 and, like its forerunners, it went heavy on the testosterone. “Booksmart” registers as an instant classic that doesn’t reinvent the genre so much as refurbish it from within, and it matters very much that the writers, director, and stars are all women. Also that they’re having a hell of a good time.

Let us now genuflect before the unstoppable force of nature that is Beanie Feldstein, who played the best friend in “Lady Bird” (2017) and who here becomes a star on her own terms. As Molly, graduating class president of her Los Angeles-area high school, she is every self-satisfied grind you sat behind in AP English. It’s the last day of classes, the hallways are a riot of orgiastic seniors, and Molly is hoping to go over school government transition plans with a principal (Jason Sudeikis) who just wants to get to his summer job driving a Lyft.

Molly’s best friend, Amy (Kaitlyn Dever), is a quieter, nerdier sort, and to the outside world she might seem a second banana. Under the direction of Olivia Wilde, a well-known actress (TV’s “House”) making a confident behind-the-camera debut, we see the tight bond of friendship that has endured since middle school and across any number of small momentous events.

Molly is headed to Yale — she pompously refers to it as “New Haven” — and “Booksmart” gets started when she learns from the school stoners and losers hanging out in the gender-inclusive bathroom that they’re all going to top-rank colleges, too. “But . . . but you guys don’t care about school,” she says with astonishment. Responds the class good-time girl (Molly Gordon), “No, we just don’t only care about school.”

Her jaw set on stun, Molly announces to Amy that “we messed up – we didn’t have fun,” and vows to crash the mega-party being thrown by her vice president and secret crush Nick (Mason Gooding), a dim but endearing class dreamboat. Amy, who came out of the closet her sophomore year but hasn’t remotely done anything about it, lusts after a chilled-out skater-girl (Victoria Ruesga). Their attempts to get to the bash become a combination obstacle course/Pilgrim’s Progress of raucous comedy, most of which rises from the character quirks of their classmates and Molly’s and Amy’s exasperated reactions thereto.

Doe-eyed and seemingly made of oak, Feldstein is a natural at both physical comedy and hairpin-turn dialogue, and she creates in Molly something new: a loveable teen dreadnought. Molly’s the kind of know-it-all who corrects the grammar of bathroom graffiti, but she has the loyalty of a centurion and a genius for invective. (For whatever it’s worth, the actress is Jonah Hill’s kid sister.) Dever has the more “sensible” role, and the laughs she gets are sneakier and more reactive but just as rich.

The tone of “Booksmart” is smutty and sweet, and the plot is often hilariously inventive. A detour to the theater clique’s mystery dinner, for instance, ends up as an accidental drug trip in which the girls morph into stop-motion Barbie dolls. There’s a visit to an empty party yacht hosted by a class rich kid (Skyler Gisondo) desperate to buy the affections of his peers. We will only mention in passing an attempted stick-up of a pizza delivery man (longtime “SNL” writer Mike O’Brien), or the hip teacher (Jessica Williams) who wants to party below her pay grade, or the brief but blissful appearances of Will Forte and Lisa Kudrow as Amy’s parents, who’ve arranged a graduation-themed dinner (e.g., mushroom caps-and-gowns) that goes uneaten.

Here’s what I love about “Booksmart” (aside from the soundtrack, which slaps): Nobody really gets hurt. The screenplay, by a quartet of women writers, understands that everyone in high school is in it together no matter how far apart their tables are in the cafeteria. At a certain point, when some of the class alpha dogs are being friendly to the heroines, you wait for the trap to spring and their cruelty to be revealed, but nope – they’re just nice. A swimming pool scene in which Amy swims ecstatically through the tangle of her classmates’ limbs recalls every moment of senior spring satori you might yourself have once experienced.

But, yes, there’s a sequence between Amy and an imperious mean girl (sort of; see above) played by Diana Silvers that involves flying vomit, just to remind us that we’re watching a stu-com. And “Booksmart” does nothing to hoist itself out of the well-worn ruts of a hermetically sealed upper-middle-class genre. Despite a few farcically surreal touches, like the exuberant class whack job (Billie Lourd) who turns up everywhere, Wilde and company have honored the rule that says everyone eventually gets home safe, and maybe a bit too much so. Nobody getting hurt can be a limitation, too.

No matter. “Booksmart” gives the girls onscreen and their older sisters behind it a chance to have fun in ways silly, salty, and magnanimous toward all concerned. Despite what the title says, it’s movie-smart, too.

★ ★ ★ ½
BOOKSMART

Directed by Olivia Wilde. Written by Susanna Fogel, Emily Halpern, Sarah Haskins, Katie Silberman. Starring Beanie Feldstein, Kaitlyn Dever. At Boston theaters, suburbs. 105 minutes. R (exuberant teenage language and behavior, including drinking, drug use, and casual sex).