Rated R

Teachers, especially those of the public school variety, have it rough. The job is difficult and thankless and teachers are at the mercy of parents, administrators and, occasionally, students. The pay sucks, the demands are impossible and often contradictory, and because they’re charged with educating children, teachers are held to a moral standard that even the most pious religious leader might find chafing. 

Somewhere in all that, there’s room for a good satire, but it’s not “Bad Teacher.” Written by Gene Stupnitsky and Lee Eisenberg (the team responsible for the 2009 bomb “Year One”) and directed by Jake Kasdan, “Bad Teacher” takes the formula perfected in “Bad Santa” and follows it joylessly to the letter. Take an innocent, sacrosanct profession, add a boozy, vulgar protagonist looking for redemption, mix in some adorable kids and see what happens. 

But Billy Bob Thornton, in all his gruff, gross glory, anchored “Bad Santa” with an equal mix of pathos and unapologetic jack-assery. Cameron Diaz doesn’t even come close in “Bad Teacher,” though she might deserve an A for effort. Well, maybe a B+. 

Diaz stars as Elizabeth Halsey, a lazy woman who’s killing time as a middle school teacher until she marries her dumb, ultra-rich fiancé. He breaks off the engagement, though, and Elizabeth’s dreams of a luxurious life are thwarted. Unsure of what else to do, she returns to school in September and sets out to find another rich man. 

One possibility is Scott Delacorte (Justin Timberlake), a sexy new substitute with a massive family fortune and an earnest, goofy personality. To get her man, Elizabeth decides she needs to get breast implants, and so she begins stealing, scamming and conniving her way to earning the $9,000 or so she needs for the operation. Opposing her is the manic uber-teacher Miss Squirrel (Lucy Punch), who disapproves of pretty much everything Elizabeth does.

Miss Squirrel gets to do a lot of disapproving. Elizabeth drinks and smokes pot while she’s at school and her entire teaching plan revolves around showing her students movies about better, more inspirational teachers (“Stand and Deliver,” “Dangerous Minds” and so on) while she sleeps off her many hangovers. And that’s all in addition to berating her students, their parents and everyone else who works at the school. The only character enamored with her is Russell (Jason Segel), an affable gym teacher who shares some of Elizabeth’s extracurricular interests but keeps all his drinking and smoking off school grounds.

“Bad Teacher” is at least a nice change of pace for Diaz, who built her early career on roles as a loveable goofball and has spent the last few years stuck in movies that are beneath her (“The Green Hornet” and “Knight and Day” are two notable examples). She swears and struts and snarls through “Bad Teacher” and it’s a fine way for her to show off her comedic chops, but it’s too bad she doesn’t have as strong or believable a role as Kristen Wiig had in “Bridesmaids.” 

Elizabeth’s shocking behavior is funny, but there’s nothing underneath the character. In “Bad Santa,” the appalling behavior is tolerable because we know redemption is at hand. But in “Bad Teacher,” it never seems like Elizabeth wants or needs to turn over a new leaf. She remains unpleasant throughout, and the predictable happy ending seems like a cheat.

That sort of forethought might be asking too much from Stupnitsky and Eisenberg, both of whom have done well as writers for “The Office” but completely dropped the ball with “Year One.” “Bad Teacher” is all over the place, with lots of flat jokes, a smattering of gross-out gags, and decently-constructed setups that go nowhere. Characters disappear frequently and, for a movie set in a school, the students hardly figure into things at all. 

Lucy Punch has some great bits of physical comedy, but she never gets the big scenes she deserves. Meanwhile, Timberlake plays against type as a dorky buffoon, but his lines seem like they belong in some other comedy. 

Kasdan directed “Walk Hard: The Dewey Cox Story,” a music-movie parody that fit in well with the Adam McKay-Will Ferrell school of comedies, and there are moments in “Bad Teacher” where that sort of anything-goes aesthetic peeks through. They don’t last long, though, and “Bad Teacher” settles for being average and unremarkable—a bad strategy for making it through school, but a perfectly acceptable one for a summertime comedy.