Sunday, October 14, 2007

Degrading on the curve

Since I believe that transparency and collaboration are values that promote student learning, I sometimes provide my students an opportunity at the beginning of the quarter to have a say about grading policies and standards. And I'm always amazed at how enthusiastic students are about curving grades. I'm opposed to curving for various reasons, but what really puzzles me is why students are enthusiastic about curves in the first place.

First off, I'm against the message about learning and achievement sent by a curve: that grades measure students against one another rather than against a defined set of benchmarks for learning. Life is competitive enough without my having to implicitly pit the students against one another. And notice that a curve gives students a rather perverse incentive not to work together on papers and assignments -- something that should be encouraged rather than penalized.

Second, I have an obligation to others that the grades I assign reflect student learning as measured against defined benchmarks. If I give a student an A in, say, a critical thinking course, a future employer has the right to infer that the student is likely to be a good critical thinker. (Yes, I realize that conclusion must be qualified in a hundred different ways, but bear with me.) But if I've used a curve that inference may not be warranted. That would be true if the student got an A by virtue of being in the top 10% of students in the course but the students in the course were extremely low achieving. In that case, the employer could infer that the student is a better critical thinker than most students, but I think the employer is entitled to make a judgment about the student's fitness for a position not just in a relative or comparative sense but in a more absolute sense — does the student have the critical thinking skills necessary for this position, period? And of course, if the employer doesn't know if I've used a curve or not, then any inferences become murkier. So given my obligations to employers, grad schools, etc., I should assign grades that don't carry a risk that students will be inadequate for the tasks or duties that employers, grad schools, etc. ask them to undertake. (And what holds for me, a mere philosopher, holds a fortiori for instructors in other disciplines: I'm pretty sure I don't want future structural engineers or surgeons graded on a curve!)

Third, I suspect that curves contribute to grade inflation, which I gather most of us think is problematic. I have no specific evidence of this, however, and would be interested to know if I'm wrong about that.

But finally, it's hard to understand the student mentality that favors curves. My guess is that students think curves are somehow less risky for their GPA's, but that's only partially true. Yes, curves ensure that some students get A's. But they also ensure that some students get F's and they cap the number of students who can get A's at all. So no matter how hard a student might work or how much she might learn, so long as a predetermined percentage of students works harder or learns more, she can't earn an A. Perhaps students accustomed to A's think that a curve will preserve their high GPA's even in the face of difficult courses. But I've found enthusiasm for curves at all levels of preparation and ability. Yet it's hard to see how curves are inherently better for students from the standpoint of their self-interest.

All this being said, I'm not averse to adjusting my grading standards on a given assignment, which could be called a mild form of curving. Sometimes an assignment proves more difficult than I anticipated, a result that might well be due to my own unrealistic expectations or my own failures as a teacher. Still, in my estimation, the benefits of curves pale next to their clear pedagogical and professional shortcomings.


  1. Michael,

    I'm very anti-curve. I have this conversation with my students as well (or at least I have in the past). Usually I tell them that I'm willing to put curves into play in the course IF they are willing to apply curves up _and_ down. So, if too many people do well on an exam (or however you want to understand the rationale behind curving), then I'll curve their scores downward.

    No one, not a single one, wants to accept that deal. And that pretty much ends the curving discussion.

  2. Hi, Michael,

    I've never used curves, for the reasons that you've mentioned (and for the additional reason that I don't assume that my students' grades on an assignment should exemplify a "normal" distribution pattern). But I'm more interested in hearing the reasons that your students want/like curves in the first place. What do they tell you?

  3. Vance,

    Inevitably, when I begin a discussion with "let's work together on some grading policies and standards," a student suggests a curve. As I suggested, their motivations are not clear to me. I wonder if part of it is they've seen the syllabus and panic: I don't think my expectations or workload are atypical, but I imagine some students might see that they're asked to write a fair bit, that they probably won't be able to get away with skipping all the reading, etc., and they decide they want something they perceive as protecting them against a set of tasks they're unwilling or unable to perform. But again I don't know, and when I make the very same observations Chris mentions, their support for a curve erodes. So I just don't know what makes them think a curve is a rational response to their situation. Maybe they've never bothered to think through the implications. Or maybe if, in their own experience, most instructors don't use a curve, then getting the instructor to use a curve is a kind of symbolic victory against "the system." But again, this isn't much more than speculation on my part.

  4. Vance,

    I'll tell you what mine say: they think curves are necessary in order to maintain justice. If many or most people do poorly on an exam, to my students that is immediate and incontrovertible proof that the exam was poorly constructed. As such, it would be unjust to hold them accountable for their scores. This is always the reason they give, I can't even think of any other ones I've ever heard. It's always the same one. That's why the "reverse curve" hits them hard. Surely, I argue, exams can be poorly written to be too easy too. An easy exam, just as much as one that is impossible to do well on, is a poor indicator of what they really know. So perhaps the scores should be curved down to reflect that, because it would be unjust to allow them to retain artificially inflated scores.


    No more curving suggestions! Now, I'm sure that for some, as Michael notes, this is motivated not by a desire to "get away with something" but rather by a fear of the class, which is probably unknown to them, and they are just looking for a "buffer". But for some, I'm afraid it is that they are looking to game the system.

  5. One thing to keep in mind as well is that the term "curve" is not used consistently throughout academia. I've had teachers who "curved" an exam by making the highest mark into a 100% (adding X pts), then adding the same X pts to everyone else's grade. This kind of grading is going to help you no matter where you're at with little to no risk. I'd imagine the students who suggest curves have something more like this practice in mind.

    Also, we have to keep in mind that while all students have been a line in a gradebook, most have little or no experience with actually giving or calculating grades. Thus, some might just know that in the past there was a curve and it helped them. That would be enough to prompt the suggestion, I think.

  6. My physics professor uses a similar method as that described by Adam Potthast above: If the class' median score is below 85, he adds points to everyone's grades until the desired distribution is achieved (i.e., median=85). This always struck me as a pretty reasonable method.

    I've never ever had a class with a "true" curve (i.e., where it's possible for a student's grade to be leveled down).

  7. This reminds me of my intro to microeconomics course. The prof gave surprise quizzes (usually weekly, he said), each of which had a maximum of 10 points. He explained that these would be curved just like all the other tests. The scoring on the (10-question) quizzes was as follows: 1 point for each correct answer, 0 for each unanswered question, and -1 for each wrong answer. He said that he felt that it was valuable for students to know what they didn't know.

    After a couple of weeks, there was much outrage, as people got back quizzes where a correct answer was undone by a wrong one. So, the prof proposed a change to the scoring. He proposed 2 points for each correct answer, 1 for each non-answer, and zero for each wrong answer. This went over very well and the class approved of it with a decisive show of hands. At this point the prof pointed out that no change had been made, since everything was being curved, and the only thing that mattered was the score in relation to all the others in the class.


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