It all began with a trip to the cinema to see Cameron Diaz in her new comedy, Bad Teacher. It was a bad choice, really. But what can I say? My editor was curious.

Not a great flick, but as a parody of bad employees, in terms of things that can get you fired—drugs, alcohol, cheating, foul language, inappropriate sexual behavior—Ms. Diaz slams pedal to the metal. You’ve probably heard: she nips out of the airline booze bottles hidden in her desk, smokes a bong in the parking lot, hands her bra to a seriously uncool kid to improve his street cred, and steals the answers to state tests.

Firing offenses? Sure, but “bad” teacher? Hmmm. Not quite. A bad teacher is different than a lousy role model. A bad teacher is someone who fails to teach, someone more like say, the teacher I had in third grade who lazed through an entire year with mimeographed worksheets and spelling tests, ignoring with equal disinterest those breezing through the too-easy work and those staring in despair at the sheets of problems.

She would stand dazed with boredom before the rows of desks, licking a finger to count out worksheets, then teeter back to her desk, kick off her heels, and pop a mint into her mouth. Those who finished early were invited to come rub her thick neck and shoulders while she noisily sucked the candy and stared out the window anywhere but at the kids sitting in abject, shame-filled misery before her.

Now that’s a bad teacher.

Anyway, thinking about this and other teacher movies I’ve seen, I began to wonder about Hollywood’s portrayal of teachers: were they quirky or idealized, sentimental or critical? And how did Tinsel Town depict “good” teachers?

So I turned to Netflix. A cursory review of the teacher film canon interestingly showed, that nearly all were biopics—To Sir with Love, Freedom Writers, Goodbye Mr. Chips, Dangerous Minds, Conrack, Mr. Holland’s Opus, Friday Night Lights, Lean on Me, The Prime of Miss Jean Brodie, Up the Down Staircase, Take the Lead, Dead Poets Society, Music of the Heart, Stand and Deliver (to name some)—all based on memoirs by educators or novels about teachers written by students.

The second thing I discovered is that, with the exception of a few, most were urban classroom-turnaround tales. The reason for this seems obvious: there is more heart-warming—and self-serving—drama in saving urban youth. These films also feed on a collective-anxiety-type drama by subjecting a fresh-faced young teacher to public humiliation at the hands of unruly teens of color. The remarkably racist trailer, for instance, for Up the Down Staircase begins with Sandra Dennis walking through crowds of African American and Latino students in Spanish Harlem as a voiceover intones: “What’s a nice girl doing in a crazy place like this?”

These fairytale stories are not unlike the depiction of student-teacher relations in another relatively recent movie, Where the Wild Things Are, Maurice Sendak’s tale of how of how a boy, Max, deconstructs evil; teacher hero disarms classroom monsters by unearthing their terrible pain, and then tames them with love and support. Earning the monsters’ respect (Max is made king!) allows the teacher to work magic in transforming raging beasts into lovable critters.

These teacher movies unspool in similar and predictable formats. They begin with the teacher’s back story of disappointment—divorce, career change, lack of opportunity— which leads to a last-minute hire into a job no one wants. The school’s principal and colleagues tell the rookie not to expect much, suggest dumbing-down texts, and warn the newbie to “watch out:” the kids are merciless.

Sure enough the class makes short work of the greenhorn who, after contemplating desertion, brainstorms how to win them over: trying unorthodox methods like games, dangerous visits to the ghetto to call on parents, bribes of candy, playing Beethoven (Conrack), or life-changing field trips against school rules to the white side of town, which entails fancy restaurants, trick-or-treating (Conrack again), amusement parks, and museums.

There are bumps along the way, but the kids are inevitably won over and, in the end, return the love. (Lulu sings an iconic tribute in To Sir with Love about how Sidney Poitier’s character brought an uncouth class of East Enders “from crayons to perfume” by demanding they show more self-respect.) In the end, the teachers discover great fulfillment in doing work that “changes lives.”

As to how well Hollywood’s depiction of “great” teachers squares with the real world, I did some fact checking to learn (no surprise here) that the demands of a compelling story arc trump the truth about the actual success these educators had in raising student achievement.

Read the rest of Colleen's online exclusive from the Harvard Education Letter.