As I wrote Monday, I dug the new film Bad Teacher. This kind of black comedy (think of Billy Bob Thornton’s Bad Santa) scrapes away familiar sentiment and can permit funny, unnerving--and frequently revealing--glimpses of human nature. Take the movie’s treatment of merit pay. Cameron Diaz’s “bad teacher,” having been dumped by her fiancée, decides she needs plastic surgery if she’s to land a wealthy husband. Lacking the $10k she needs, she pockets cash from an R-rated middle school car wash and bribes from parents at parent-teacher night. When she learns that there’s a $5,700 cash bonus for the teacher at John Adams Middle School whose class scores highest on the state test, she turns from a burnout serial-movie-shower into a motivated (if inept, mean-spirited) instructor.

As my friends at NCTQ have pointed out, the merit pay scheme in question bears little resemblance to what actually exists. Far more interesting, though, are the truths it tells about merit pay. After all, today’s vaunted merit pay experiments (think Nashville or New York City) basically offer cash in return for good test scores. This may be a dumb and unhelpful way to approach differentiated pay--for my own take, see here or here--but there it is.

Bad Teacher offers the most straightforward accounting of the underlying assumptions of paying-for-scores that I’ve yet seen, in print or on screen. A lousy, unmotivated teacher who desires breast implants is inspired to work much harder to earn the cash. There you go: honest, straightforward, incentive-driven--and utterly disinterested in social justice or the larger purposes of schooling. She changes her behavior because there are rewards for doing so. There’s no expectation that the change is permanent, that it alters the content of her character, or even that she’ll teach any better--only that she’ll teach harder. And, it should come as no surprise that she looks for an opportunity to cheat when her other efforts aren’t getting it done. At the same time, for all these thorny issues, I’d absolutely argue that her kids are better off after she learns about the bonus than they were before.

Yet, many merit pay champions seem bitterly disinclined to talk honestly about any of this. They don’t want to discuss the limits of cash-for-scores, ignore perverse incentives, are shockingly cavalier about possible cheating, and blithely presume that there are no larger implications when a teacher is motivated by the lure of top-shelf plastic surgery. Instead, merit pay enthusiasts merely prattle that this is all “for the kids” and pretend that such policies easily coexist with their grand ambitions of recruiting educators fueled by an evangelical commitment to serving the poor and downtrodden.

There are contradictions, complexities, and tensions here that are hardly ever addressed. Me, I’m fine with self-interest, think it’s a mistake to place too much emphasis on rewarding teachers based on today’s test scores, and therefore will reiterate that I ardently support differentiating pay based on work and role--with student performance constituting one part of that.

The bigger point, especially for those of you supporting rethinking pay, is that there are downsides and unanticipated consequences which are too rarely addressed. Figuring out how to do this well is a helluva lot tougher than most policymakers and self-proclaimed reformers think. And I wish our debates about merit pay were as attentive to motivation and potential conflicts as Cameron Diaz’s risqué popcorn flick.