Requesting All Student's Grades From Professor
Is it unreasonable for the student to request a list of all other students grades from the prof to verify that they were actually in the bottom 15%?
Yes, it's unreasonable. It's perfectly fine to ask something like "My reading of the grading policy is that only the bottom 15% of the class receives a D or below. Is that correct, and is my grade of 78 really in the bottom 15%? I felt I was doing better than that, so I'd like to check that the D is correct." Requesting the other grades themselves offers no more assurance that it's right (the only situation where it really helps you is if the professor just isn't capable of computing 15% correctly), it's more work for the professor, and most importantly it leaks information about how other people are doing. For example, one of the top students in the class could use this data to make a good guess as to whether their rival had outperformed them or not. The particular risks here might not be a big deal, but at least in the U.S. grades are considered private and should not be revealed.
The request is not unreasonable, though privacy concerns may make it not possible, particularly for small classes. But this is a problem with the grading method, not the request. The student should be given some information about the grade distribution, or might reasonably request that an administrator or authorized party other than the professor confirm that the grade was calculated correctly and the grading is fair.
As a professor, I think that my students have an absolute right to understand how their grade is calculated. If I make that calculation depend on the distribution of grades in a class, then I've imposed a requirement on myself that my students have a right to understand that distribution, even if they don't know who earned what grades. If I want to obfuscate exact scores as an additional measure of privacy, I could show just a histogram, or announce the mean and standard deviation of grades.
If the student were not given this information, there are two very serious concerns:
- The student can spend the whole semester thinking they are performing adequately, only to find out that they were misled. To get a grade of D, the professor must think that student has exhibited a bare degree of competence, and is not ready to advance to higher level material. If the student was clueless earlier in the term because their numerical score indicated they were performing at a high C (what a 78 translates to in most American institutions), that student has not been served well by the course.
- Grading the student based on hidden information opens up the possibility that a professor could lower a student's grade for reasons not related to the student's performance (personal dislike, unconscious bias, etc.), and the student would have no way of verifying.
In courses I have taken as both an undergraduate and graduate student (in American institutions), when exams or courses were "curved" (i.e., graded in relation to the distribution), the professors would always give us some summary statistics (such as the mean score, or number of students in each letter grade bucket). As a professor, when I have curved an exam, I also would provide information on at least the mean, and maybe some other summary information as well. No one has ever indicated to me that this violates privacy requirements. But if, say, an administrator told me that I could no longer do that because of privacy concerns, then it seems that a faculty advisor, department chair, administrator, or someone else with appropriate authority to review private student records would have to be given access to all student grades in the course so that a student would have recourse if they suspect they have been graded unfairly (point 2 above).
I have to also say that in my experience when student grades are based on the distribution of other students' scores, it usually means that grades are raised relative to what they would have been using an absolute scale. I have not heard of someone using the distribution to lower final grades relative to what they would have been on an absolute scale. I never experienced it as a student (and would have been unhappy if it happened), I wouldn't do it as a professor, and I have not heard of colleagues doing it in their courses.
In summary, although it was not part of the original question, I think it has to be said that this grading system is pedagogically unsound because it seriously impedes the students' ability to understand their mastery of the material prior to the assignment of the final grade. Be that as it may, because the student has a right to understand how their grade is calculated, and in order to avoid the possibility of the professor assigning arbitrary or unfair grades, if this is the way a course is going to be graded, the professor has imposed upon themself the duty to publicize some information about the the distribution of scores in the course.
It should also be checked if students were notified at the start of the semester that rank statistics would be used to assign grades. If not, that's likely more than enough reason for having the grades checked, since most schools will have a grading standard that says 78% is equivalent to a C or C+, not a D.
Also, while you, as the tutor, have no right to ask for a list or histogram of grades, the student has the right to know where they stood in the class overall relative to the various demarcation points, and what was the scheme used to assign grades. However, as pointed out, they don't have the right to ask for all of the numerical grades.