Grading curves in quantitative subjects In U.S. colleges, in quantitative fields of study like engineering and mathematics, how do instructors curve their courses?  That is, how do instructors decide, in a given course, how many As to award, how many Bs, how many Cs, and so on?

I do not ask the opinion-based question of how an instructor should curve his or her course. Rather, I ask the fact-based, or at any rate experience-based, question of how a normal, responsible, experienced instructor does curve his or her course.
I do not ask the opinion-based question of how an instructor should curve his or her course. Rather, I ask the fact-based, or at any rate experience-based, question of how a normal, responsible, experienced instructor does curve his or her course.


I think the following would be a typical story of the process. Jane is hired to a tenure-track faculty position in physics, and she is going to teach freshman mechanics her first semester. To find out what is considered the normal academic level of the course at this school, she looks at available information such as the text being used, the lab manual, the problem sets assigned by previous instructors, and, if possible, exams set by previous instructors. She looks at myedu.com to see histograms of grades given by other teachers at this school in this course.

Based on this information, she tries to set standards that will seem somewhat easier than average at this school. She wants to make sure that her grading isn't seen as too harsh, which could result in poor teaching evaluations and endanger her hopes of tenure. She can't afford to be as stringent a grader as some of the senior faculty, because she's not insulated by tenure as they are. She can use an infinite variety of factors to adjust the level of difficulty, but she is constrained by this need to appear a little more lenient than average.

In most cases, people end up teaching at schools that are less selective than the ones at which they got their own degrees. This is the case for Jane, so after the first midterm she finds that her best attempts to be perceived as a lenient grader are failing rather badly. Many of her students are very upset. Jane is alarmed. She has recently acquired a mortgage, and a terrier that everyone says looks like President Trump.  If she doesn't get tenure, she and the dog will be out on the street. She makes further downward adjustments in her standards. Within a few semesters, she arrives at a set of standards that become the ones she considers normal for the rest of her career as a "normal, responsible, experienced instructor."

Jane gets tenure, and as time goes on, more tenure-track faculty members are hired in her department. These new folks go through the same process described above, arriving at standards that are in turn incrementally lower than the ones Jane uses. This trend continues over the years. By the time she retires, Jane owns a bulldog that everyone says looks like President Bannon, and she has become legendary as an extremely harsh grader compared to her younger colleagues.

For more on this topic, see:

Arum and Roksa, Academically Adrift, 2011

Valen Johnson, Grade Inflation: A Crisis in College Education, 2003