Plus/Minus Grading Systems

Have you ever thought about the pros and cons of our plus/minus grading system versus the A-B-C-D-F system employed by other universities? The plus/minus system actually has several advantages—see for example the reasons RPI adopted a plus/minus system in 2004.

Despite the advantages, under a plus/minus system I’m finding it challenging to implement something I learned from Ken Bain in 2007.

In his 3-day Best Teachers Summer Institute, Bain leads a unit on assessment. In particular he asks educators, “What does it mean for a student to be an ‘A thinker’ in your discipline? What must students be able to demonstrate or do to live up to that standard? How would it be measured if there were no such thing as numerical grades?” Bain suggests that we share with students our answers to these questions to help them understand what it takes to be a so-called A thinker.

When I did Bain’s exercise, I learned that the definitions for A vs. B vs. C thinkers are not trivial, but doable. But consider this. Our plus/minus system has 11 grade categories whereas the A-B-C-D-F system has 5. It’s been 3 years, and acceptable definitions for each of the 11 brackets still elude me. What is it exactly that a C+ thinker can do that a C thinker cannot?

If you have found good ways to define plus/minus grades in the spirit of delineating what students demonstrate they can do (rather than numerical scores), I’d like to hear from you. What works for you?


Here’s another issue with our grading system that borders on triviality, but, well, I think about these things. Suppose in a jumbo lecture an instructor gives 3 multiple-choice exams, averages the scores, and (voilà) assigns final grades according to the chart in the faculty handbook. In our plus/minus system, if we assume the course scores are uniformly distributed between 50% and 100% (which they are not, but bear with me), then 10% of the students are expected to be a half-percentage point below a cutoff, inviting natural rounding up. That is, 1 in 10 students may be arguing for the next higher grade, a grade they technically didn’t achieve. Maybe the number is not exactly 10%, but it’s close for many reasonable grade distributions.

Certainly, there are all sorts of considerations when resolving the rounding question, but that’s not the point. The issue is the sheer number of “rounding cases” that our grading system invites. I recently taught a course where 21% of the final scores were less than a half point below a cutoff.

Happy 2010 everyone.

This entry was posted in Assessing Learning, Grading. Bookmark the permalink.

4 Responses to Plus/Minus Grading Systems

  1. Elisabeth Gareis says:

    Thank you, Will, for another thought-provoking entry. The difference between ABCDF and plus/minus grading reminds me of the difference between learning goals and objectives. The first addresses larger standards, the other more specific measures of effectiveness.

    When I was a student teacher at a high school in GA, we had to create very specific objectives for each lesson. Each objective had to focus on outcomes, and contain details and a standard. I taught foreign languages, and an objective might read: “Students will be able to describe in writing their activities during a recent weekend, using the past tense form of at least 10 irregular verbs with 80% accuracy.” That is, only if all students used at least 10 verbs and made a maximum of 2 errors was the lesson considered a success. If they didn’t, the teacher had either set the bar too high or hadn’t taught effectively.

    Objectives for form are easier to create than for content, but with the help of rubrics, even content and higher-order skills can be evaluated numerically. If each element (e.g., content ranging from superficial, to rudimentary, generally competent, more than competent, and rich) is defined and exemplified, grading can be very reliable. And when all of a student’s grades are added up at the end of the semester, the result should reflect the student’s level of excellence.

    Also, if students keep records of their own performance during the semester, they’ll know if they are approaching a cusp and can make an extra effort to reach the next grade level.

    If there is a disconnect, it’s most likely at the junction of discipline-wide standards (Bain’s “A thinker”) and specific lesson or assignment objectives. If it is a larger goal in a discipline, for example, for students to be interculturally sensitive, how are we assessing the achievement of that goal? And what are we doing in our day-to-day classes to address that larger goal?

  2. Arthur Lewin says:

    These are some thought provoking questions to wrestle with. In addition, I was struck by the terminology, ‘A thinker.’ Is the term ‘A thinker’ a synonym for ‘A student?’ But how could it be? Don’t grades also measure memory and other attributes besides thinking?

  3. MEdwards says:

    Excellent post and I agree with Will’s sentiments. I wonder, though, about the potentially pernicious, unintended effects of a five-grade system (not that Will was endorsing such a move). I won’t try to tease out all of the implications, but this system might raise the stakes for each individual course grade leading to some unfortunate faculty and student behavior. And then we run into the whole “socialism in one country” problem–with all of the problems caused by having a system in place that differs from other schools.

    BTW, I was at UW-Madison for 2 years in the 1980s and they had an A, A/B, B, B/C, etc. system, which I thought was quite reasonable.

  4. Greg Parks says:

    The plus minus system can put students at a disadvantage and I can see in no way how the plus minus system helps the students. An example is a student who only scores one 91 and the rest 95s in the rest of the classes while working on a degree. In the plus minus system that student can never have a 4.0. Meanwhile the student from another university, which does not use the plus minus system, with all 91s in every class will post a 4.0 GPA. Now both of these students apply for the same job. If everything else is equal, the student with the 4.0 will get the job.
    The only argument an administrator could give me in defense of this situation is GPAs don’t really matter. My counter to that is then don’t post a GPA.
    I think the plus minus system only benefits University’s overall GPA. Wait a minute, did I just suggest that a University cares more about itself than the student?

Comments are closed.