Why does this movie exist?

Rating: 1/10 (13 November 2012)

Just watched Bad Teacher. WHO ALLOWED THIS MOVIE TO BE MADE?! I watched it mostly because I really like Jason Segel and sometimes Cameron Diaz isn't terrible. But this movie... I'm not sure why this movie exists.If you're not familiar with this "film" I envy you.
It stars Diaz as a crappy, disinterested junior high school teacher named Elizabeth. Her only goal in life is to marry a rich guy and spend as much of his money she can. The movie starts out with her leaving her teaching job, after one year, to marry a rich man, he wisely dumps her and she goes back to being a teacher until she can snare replacement wallet. The next school year starts out and she does nothing but show her class, she seems to have only the one class, movies that somehow incorporate school (Lean on Me, Dangerous Minds, etc.). She meets new teacher Scott, played by Justin Timberlake, who happens to have a rich family and decides that what she needs to snare this man, based on a picture of his ex, is bigger boobs. To do this she needs about $10,000. Hard to achieve on a teacher's salary so she volunteers to help with the school's car wash fundraiser and dresses like a slut in order to earn extra "tips" from pervy guys. All the while she is being pursued by Russell (Jason Segel), a gym teacher at the same school, whom she ignores because he's just a gym teacher. She also does what she can to appeal to the naive and stupid Scott who is interested in Elizabeth's rival Amy who does whatever she can to expose Diaz as a marijuana-smoking-in-the-parking-lot crappy teacher. Elizabeth learns that she can earn a $5700 bonus if her students get the highest scores in some standardized test. She tries to be a real teacher in order to get her students to pass but when it becomes apparent that this tactic will not produce the results she desires she seduces and drugs and employee at the testing company in order to steal a copy of the test. Her students end up getting the highest scores and she gets her bonus check. Amy discovers what she's done, after almost being poisoned when Elizabeth rubs poison ivy on an apply that Amy eats and Elizabeth steals her boyfriend Scott, and turns her in. Elizabeth blackmails the test company employee and escapes those charges. Amy then uses the drug use as a way to get Elizabeth fired. That backfires as well and Amy takes the rap for the drugs in Elizabeth's desk. Amy is sent to a school full of troubled teens, Elizabeth blows of rich guy Scott and hooks up with Russell. All the while never learning a single lesson. She gets away with all of the horrible things she's done and the good teacher who actually cares about teaching gets punished.
Seriously?! This is the message of the movie? Lie, cheat, steal, drug and blackmail people, only be concerned with how much money somebody has, bigger boobs will make you happy, treat kids and your coworkers like crap, smoke pot, poison coworkers, use inappropriate language around kids and just be a bitch. That's what Bad Teacher taught me. This is a horrible movie that shouldn't even exist.