It's hard to grade a non-research paper that way though. For example, that class was a Humanities 101 class. We were supposed to do some analysis of whatever book we'd just read. So good grammar is not a large part of the grade, and factual correctness is not easy to check when you could "hit the stacks" and cross-reference any other books in the library. The teacher (who was good by the way, I'm blaming the system not him) would grade the paper based on how "good" he felt it was, based on your apparent understanding of the material, and your ability to think well and express your thoughts clearly.
There is also a lot of bias in this though. I have an interesting anecdote from this, one I'm not so proud of... For the first half of my writing 101 class I got a B-/C+ on every essay I wrote ~3-4. Then I took my girlfriends at the time "creative writing"/poem or whatever the assignment was and my teacher went bonkers about it thought it was better than sliced bread, tried to get me to take a creative writing class (which I milked and was like yaa i'll think about it). I wrote every paper after that and consistently got 95+ on them. Interestingly in the last paper one notable comment from her was "Your content is brilliant! your analysis of the book and your thoughts are the subject are amazing! however be careful with your sentence structure and grammer it detracts from the paper" I got a 97 on this and I put basically the same effort on this paper as I did in the beginning.
This is simple human bias if you expect something to be good it will be good, and has to do with how your teacher feels about you.
Ya, many of my English papers are graded on factors like thought and understanding, supporting evidence etc. While, these are still subjective, for these and the measures you were marked on, it much easier to explain what a five out of five, what a four out of five is etc. rather than say effort. But, ya, it's way harder to come with fair, objective criteria for Humanities papers. (At least it is for my experienced high school mind)
It's hard for everyone. He was one of the deans of a liberal arts college, and had had a paper published in Dickens Quarterly. So he really knew what he was talking about when it came to writing humanities papers. But in the discussion we had on grading, he admitted that there were very few rules. He would try just to be fair.
Your consistent B- grade was a measure of the class, not your work. Sorry that the world is so unfair, but humanities courses (particularly 101 level) are rife with this.
I once got an A in a philosophy course where I never even turned in any work. I think the teacher knew I was generally smart and argumentative, and just gave people marks accordingly.
Did you get data on how other students did? I received an A in a science/tech/policy class which I didn't do half the assignments for. Talking around a bit, everyone else I knew got an A as well.
I recall seeing a posted list that related student ID numbers to grades. I think I would remember if everyone got an A. Because I felt so guilty about that A that I did the assignments and turned them in, after the fact. The class was about morals and ethics, and the irony bothered me.
I wouldn't do that today, because I'm more aware of how irrelevant school is.