New York • The last time we left "Mean Girls," in those clique-obsessed classrooms at North Shore High — well, actually, in Washington's National Theatre — the musical's creative team, led by nonpareil comedy writer Tina Fey, was facing some major homework. The score by Jeff Richmond and Nell Benjamin contained some serious misfires, and several of the central characters seemed marooned from the kind of precision-guided character-delineating material a satire of adolescent social cruelty has to feature.

So here this show on choreographic hyper-drive lands, five months later — and what an enjoyable completion of the assignment the creative team has handed in, all to the benefit of your experience in the modern Darwinian teenage zone of mock-or-be-mocked, of dress-to-kill-or-be-pilloried.

As a result, the "Mean Girls" that had its official opening Sunday night at Broadway's August Wilson Theatre with a cast and cadre of designers intact from the Washington tryout, is a well-tooled winner, and not just for younger audiences who imprinted on the 2004 film with Lindsay Lohan and Rachel McAdams. Fey's script, evoking the best of her contributions to NBC's "30 Rock," is tailor-made for any adult ear that grooves on mischievous wit, and director-choreographer Casey Nicholaw, a veteran when it comes to Broadway's impish impulses ("The Book of Mormon," "Monty Python's Spamalot"), knows exactly how to spin a musical into an orbit fueled by hormones gone haywire.

True, the gyrations here become a bit frantic at times, and the frequency with which the singers go for broke on the tippy-top notes of their power ballads seems overly calculated to pump up the appreciative ovations. But hey, they're kids, right? You can talk and talk till your face is blue. Kids! But they still do just what they want to do! And in any event, the "kids" on this occasion are all sparkling comedians, and among the funniest, two in support who just might walk away with Tonys: Kate Rockwell as the dullest tack in the pack, Karen, and equally gloriously, Grey Henson as Damian, the drollest gay high schooler this side of [your favorite acerbic character here].

They and the other players wear as second skins the tribal rituals of American secondary-school society. Around two of them the story revolves, as in the movie: Erika Henningsen as Cady, the nice girl, a social tabula rasa who transfers in from a childhood in Africa, and Taylor Louderman as Regina, the fashionista alpha girl who rules the cafeteria the way Putin dominates the Kremlin. The plot is driven by the impact they have on each other and the collateral damage their escalating war inflicts, on neurotic followers such as Gretchen (Ashley Park) and wounded rebels like Janis (Barrett Wilbert Weed). All are remarkably good, and clearly have investigated more deeply who these characters are, because at the conclusion of 2½ hours of exuberant Broadway-style pop and hip-hop, the feel-good resolution actually now does make you feel good.

The added appeal owes in part to the commitment that Richmond and Benjamin have made to fixing the score. All four major-milestone moments of the musical—the numbers opening and capping both acts—have been changed, and the impact shows. Gone are the particularly weak Act 1 finale, "Justice," and a forgettable Act 2 opener, "Bossed Up": They've been replaced by the more pleasing "Fearless," which has new lyrics set to the tune of "Justice," and by "Stop," a bracing new song after intermission that finally gives Henson the big number he deserves. (OK, it does incorporate that dance ingredient that has become all too de rigueur on Broadway — I'll let you find out for yourself — but you will be happy with what Henson does with it.)

The show's first 30 minutes remain a golden half-hour, with a smoother integration of the gentle narration by Janis and Damian, and leading into a reworked and still wonderfully clever transition from the wilds of the savanna to the wilds of the campus. The transformation of Henningsen's Cady is more deftly handled now, and solo numbers for Regina, Gretchen and Karen have in various cases been tweaked, or reset, or are now delivered with more slyness and polish. And I can also report that a bland song for Regina's outrageously indulgent mother, played by a winning Kerry Butler, has been replaced by a funnier number, a duet for her and Gretchen.

Richmond's pop-standard compositions serve Benjamin's sharp lyrics well, and Fey has put in a bunch of new jokes, a few of them cheekily topical, and a couple of bluish ones, as she is wont to write, that draw nervous giggles. She has also newly restored a gag or two from the movie: Recall, if you will, that frisky terrier in the arms of Regina's mother, Mrs. George.

And yes, for sure, "Mean Girls" is a chronicle on the superficial side: Some lip service is paid to the evils of bullying, but the evening is pure sendup. That it's a showcase for so many gifted young comic actresses is no minor blessing; and the guys, like Kyle Selig, as the requisite dreamboat, and Cheech Manohar, as the geeky showboat, are strong assets, too. Visual panache is supplied by Gregg Barnes's drop-dead costumes and the graphics-driven backdrops by Finn Ross and Adam Young. Best of all, in a marketplace filled with mindless work about teens, here's one that doesn't insult their intelligence — or yours.