"Bad Teacher" doesn't make the case for worst film of 2009, but it doesn't really go much above mediocre. The "hero" of "Bad Teacher," Elizabeth Halsey (Cameron Diaz), certainly could make the case for the worst teacher in America. Rather than actually teach her students, she shows them films like "Stand and Deliver" and she frequently smokes pot in the school parking lot.
Also, she uses men for their money, and couldn't care less whether or not her students are learning. She instead aspires to scam the school out of enough money to pay for a new surgery she wants to get in order to impress a new teacher, Scott Delacorte (Justin Timberlake). A chirpy, overachieving teacher (Lucy Punch) tries to sabotage Ms. Halsey's plans.
"Bad Teacher" is a movie in which nothing deserving happens, neither to the characters nor the audience. Comedies are fueled off characters who do bad things, but it is not enough to just be a bad person. In "Bridesmaids," Kristen Wiig might say some terrible words to a young girl, but at least she wanted to open a bakery. Elizabeth Halsey, meanwhile, only does actions to serve herself. Once she has the chance for redemption, it barely feels earned.
Yet, the bright side of "Bad Teacher" lies most in its undervalued supporting cast. I would have preferred to see a movie about the chipper Ms. Squirrel, played by Lucy Punch. She gives off more personality and is funnier in one scene than Diaz is during the entire movie. Jason Segel steals many scenes as the school's gym teacher. Timberlake, meanwhile, is surprisingly bland for an actor who is usually so energetic.
The reasons that Diaz's teacher is so easily hatable isn't just because of her lack of interest in her job as well as her ability to use people; that was intended. The other reason is that Diaz doesn't make her character even worth giving a chance. Nefarious characters are meant to be looked down upon but they don't necessarily have to be totally despicable. Characters doing bad things can often be ground to even more humor. Yet, Halsey is given so little charm or charisma that her crimes aren't even entertaining to watch. Each one is just an excuse for her to get to her ultimate goal. The moment her character decides to turn around is basically a ripoff of a scene from "Billy Madison." And stealing from "Billy Madison" is unacceptable.
I believe that most comedies (the high concept ones, mainly) run on karma, and characters becoming liked because they change. "Bad Teacher" follows neither of these as it punishes rewarding characters and doesn't really change the bad ones. In its attempt to be dark and edgy, "Bad Teacher" fails as a possible black comedy. It is impossible to ever be funny or edgy when anything in your movie that could possibly be funny or edgy is revealed in the trailer.