If Bad Teacher is a vocational reworking of Terry Zwigoff’s masterful Bad Santa, with Cameron Diaz’s lazy, money-grubbing, breast implant-seeking schoolteacher filling in for Billy Bob Thornton’s lazy, money-grubbing, alcohol-seeking mall Santa, then it’s a curiously tepid cousin needlessly sanitized by its good intentions. Diaz’s Elizabeth Hasley drinks bottles of whiskey hidden in her desk drawer, bluntly informs a kid who wears his abandoned father’s sweatshirt several times a week that he has no chance with the prettiest girl at school, and embezzles money from the seventh-grade car wash (shortly after using her body to spike up the funds and causing a police car to crash)*. But Hasley isn’t mean and interesting in the way that Billy Bob’s Willie T. Stokes captured our attentions. Instead of having a fast-talking dwarf Marcus as a sidekick, Hasley has the passive Lynn Davies (played by Phyllis Smith, best known as Phyllis from The Office), who looks forward to her three months off in the summer (with numerous trips to the zoo) and sees a surprise milk choice at the cafeteria (“2%? 1%? Chocolate?”) as a high point. What Bad Santa understood was that having a seemingly modest character constantly criticizing a middle-aged loser made us more interested in why the latter lived the way that he did. Hasley has no such luck with Lynn. Indeed, it’s Hasley who is the one to encourage Lynn to talk with two cowboys at a bar. Which works against the idea that her character is supposed to be, well, bad.

Perhaps screenwriters Gene Stupntsky and Lee Eisenberg (both veterans of The Office) should be faulted because they’ve been working too long within the needlessly restrictive limits of American television. They don’t seem to understand that an R-rated movie featuring a mean character really should be dangerous, but their floundering wit is here in spurts. There’s one funny moment early on when Hasley’s man shouts about the need for opera to be passed on to the next generation. And when Bad Teacher was especially irreverent, such as Justin Timberlake’s squeaky-clean teacher making racially insensitive remarks about a new Ethiopian restaurant or an especially aggressive method of getting kids to remember the details of To Kill a Mockingbird, I longed for the film to transcend into additional cringe comedy. But then the film would present another weak or gutless or repetitive moment, not understanding that incriminating photos of a naked administrator or Lucy Punch’s chirrupy Amy Squirrel getting a few comeuppances were mere variations on hackeneyed comic situations we’ve seen too many times before.

Jake Kasdan’s flat direction is also a big problem. I don’t know what has happened to Kasdan ever since his fine work on Freaks and Geeks and his very underrated debut feature, Zero Effect, but I fear that Lawrence’s son is now a lost cause. I’m fairly certain that Cameron Diaz was slightly miscast, but I don’t know for sure. Because she delivers her lines with heavy aspiration on the consonants rather than hitting the vowels hard. And because Diaz’s voice is mellifluous, this disastrous direction causes Diaz to lose the authority she so desperately needs to win our attention, especially because Hasley is rejected by several men when she tries to use her looks and she’s someone who spends cash so wantonly. And while I recognize that Justin Timberlake has about as many dramatic options as a home pregnancy test, a good director will understand that mixing up the only two settings available (as David Fincher did in The Social Network) is better than sticking with one. There’s something deeply unpleasant about seeing a 30-year-old guy who believes he’s in sync with Stanislavsky resort to the same terrible stage-hogging case of the cutes that he used in his twenties. Sure, Timberlake isn’t much of an actor. But can’t he at least pretend to be an adult?

The one actor I can commend here is Jason Segel as an underestimated gym teacher persistently trying to woo Hasley. I liked Segel in Knocked Up and Forgetting Sarah Marshall, and he seems to be the only actor in this movie who is having any fun, perhaps because he knows how to use his face to suggest a social awareness that other characters lack. But Segel isn’t a mugger: he knows how to enter a scene without dominating it and he knows how to make his fellow actors look good. If we’re not drawn to Cameron Diaz in this movie, then Jason Segel serves that role.

But enough about Jason Segel, who hardly needs any help from me. In our post-Bridesmaids landscape, the time has come for women to be rude, crude, mean, and dangerous in mainstream comedies without being kept on a leash. Bad Teacher cannot live up to this basic requirement, and, in failing to be even modestly subversive, it becomes an instantly regressive and instantly forgettable offering.

* — A brief note on this movie’s recidivist exploitation of the physical female form: If Bad Teacher has been designed in any way as a double X counterweight to male-dominated comedies, why are the filmmakers here so desperate to use Cameron Diaz’s body like this? Furthermore, why does she seek a breast implant rather than cold hard cash? Still furthermore, in an opening scene, there is one fellow teacher — a slightly overweight (that would be “normal” weight) woman played by Jillian Armenante, whom I remember playing a sensitive therapist from The Sarah Connor Chronicles — who appears, expressing enthusiasm. She raises her arm. We see the sweat spots in her armpits. And that’s it. There is an additional moment when a woman’s breasts are there to be ogled for their silicone perfection by all and sundry. And that’s it. I submit to the reader that a movie that maintains such a superficial interest in women instantly loses credibility, especially when Eisenberg claims in the production notes: “We would see so many funny women on Saturday Night Live and on talk shows, and they’d be hysterical and charming, and then we’d go to the movies and they’d be props to get two guys to become friends or whatever. We really wanted to write a project for a comedienne.” Eisenberg may have wanted to write a project for a comedienne, but the film clearly views much of its supporting women as props.