There are some teachers who employ this sort of normalization and then give "A"s to a certain percentage of students, "B"s to a certain percentage, and so on. I deplore the use of such quotas - the simple fact is that I have seen classes in which over half of the students did outstanding work and deserved "A"s, and I have seen classes in which very few met the expected level of performance (B).

Therefore, I use the normalized scores as described above simply to place students into a statistically valid ranking. I examine the total work turned in by students at various points within the ranking to determine whether that student has performed overall at an level of meeting my expectations for anyone successfully completing the course (B), exceeding those expectations (A), failing to meet those expectations but demonstrating enough competance to move on to subsequent courses (C), etc. This establishes the bounds for each letter grade within the overall class rank, and the remaining students cane be assigned letter grades accordingly.

Is the final process of assigning letter grades a subjective one? Of course it is, but all letter grading is subjective, and to claim otherwise would be intellectually dishonest. Any instructor is expected to have enough professional expertise to judge what constitutes acceptable, poor, and good work. The only real question is when they exercise that judgement.

Instructors who employ the 100/70 rule are being subjective, first in choosing the 70% threshold and then again in designing their assignments and tests to meet that rule. Instructors who employ quota systems are being subjective in establishing those quotas. I prefer to withhold my subjective judgement until the assignment or exam results are in, when I have the most information available on which to base my decision.