Movie review: ‘Bad Teacher’

“Bad Teacher” is a classic underachiever. This subversive comedy definitely has its moments, but when the final grades are in, the raunchy romantic romp starring Cameron Diaz, Jason Segel, Justin Timberlake and Lucy Punch is a frustrating mix of smart flash and smirking impudence. It makes you want to dash off a “could have been great, if only they’d tried harder” note to the parents.

The notion that director Jake Kasdan and screenwriters Gene Stupnitsky and Lee Eisenberg (“The Office” veterans) play with is a clever twist on the age-old question: What really makes a good girl good and a bad girl bad? I say “girl” because even though Diaz’s Elizabeth Halsey and Punch’s Amy Squirrel are board-certified teachers, they are a long way from adults. Ironically, Segel’s pot-smoking gym teacher is the grown-up among “Bad Teacher’s” class clowns, and quite an appealing one at that. Meanwhile, Timberlake is an embarrassingly infantile sub, Mr. Delacorte, though he can sing (but we knew that).

Now to the “good-bad” question, which the filmmakers have restated thusly: Can we look past Elizabeth’s filthy mouth, very hot bod, fabulous hair, sexy clothes and clear disdain for virtually all of humanity to see the possibly decent person that might be buried deep, deep, deep inside? They don’t make a “yes” easy.

The movie starts as Elizabeth is wrapping up what she thinks will be her first and last year at the local middle school, where she’s been putting the finishing touches on her wedding of convenience — her intended is conveniently rich. A bad turn of events puts her back in the classroom in the fall and convinces her that all she needs is a boob job to turn things around. Raising enough money for the procedure becomes an obsession and she will do anything to get there. The various “anythings” become the comic fodder that drives the action, with cinematographer Alar Kivilo (“The Blind Side”) ensuring that the apple stays polished.

Elizabeth’s nemesis is Amy, a perky redhead who’s got a killer grip on the top teacher spot, a crush on goody two-shoes Mr. Delacorte and an increasingly loose screw. Driving her crazy is Elizabeth’s ability to convince everyone else that despite her many offenses — showing movies to her class while she sleeps off a hangover is a frequent one — she’s good at her job, or as Principal Wally Snur (John Michael Higgins) puts it, she’s teaching “for the right reasons” (which sadly only makes me think of “The Bachelor” and “The Bachelorette”).

Diaz is quite fearless in playing funny, willing to throw those long gams and all that sex appeal under the bus if it will get the laugh. It’s been more successful when she’s playing the innocent, as she did with a great deal of campy charm in “There’s Something About Mary” and “My Best Friend’s Wedding.” She should be able to go dark too, but most filmmakers, including Kasdan, don’t seem to know exactly how to take her there. So, instead of physical comedy (soaping up in Daisy Dukes at the school’s fundraising car wash does not count), “Bad Teacher” puts all its comic chips on giving her a potty mouth.

I guess in the current comedy culture where F-bombs are king, it’s good that Hollywood is finally allowing women to be just as foul as the guys, though I don’t think that’s what the feminist movement had in mind with the whole gender-equality fight. That the filmmakers find the idea of a woman saying something really blue to be both shocking and fall-down hilarious tells you just how far we have to go.

Though perhaps not a lofty goal, hard-R comic equality is possible in the best sense. Case in point: “Bridesmaids” served up its women raw, but if you watch it closely, the raunch has organic roots planted in situations. “Bad Teacher,” on the other hand, uses more of the strafing approach — having Elizabeth throw bad words around like Molotov cocktails whenever things get slow.

That approach helps make “Bad Teacher” feel more like a string of comic vignettes than an actual story unfolding, more heavily influenced in style than it should be by the writers’ sitcom background. A few of those short bits, though, are priceless, especially the interludes that pair Diaz and Phyllis Smith, playing a dandy version of the self-deprecating soul that has made her such a valuable member of “The Office” ensemble.

As a comedy director, Kasdan has good instincts that aren’t quite fully realized here. The scenes that are the most satisfying — Diaz and Segel’s romantic smackdowns chief among them — are the ones that are more character-driven, echoing the fine work he did on TV’s “Freaks and Geeks” and “Undeclared.” Unfortunately, there aren’t enough of them to keep you from wishing that school would let out early.

betsy.sharkey@latimes.com