I think the different attitudes about grading are interesting. I went to a high school that didn't use grades so maybe it just makes sense to me that the whole system(s) is invented. A C here (US) is meant to be "average" and a B "above average" and an A "excellent" which is why some teachers grade a on curve, because those terms imply your position within the class.
I see there being two ways to think about a grade, either it represents your performance in a class. Did you show up, did you listen to the professor, did you read the assigned reading? In that case people should be capable of near 100% grades, points off for mistakes, points off for that topic you didn't understand, points off for that class you missed... Most people in a class will still get over a C. On the other hand a test could grade your understanding of a topic, in that case to get near a 100% you would need a lot of outside reading and studying. Instead of making sure someone has the basics down, and understands the key topics of the lectures, you are testing the position of their understanding within the field, so it is unlikely you could get an A, because even if the test is limited to introductory topics you won't know most of them after one semester. Say an intro to American Lit class. You wouldn't even know the major authors of all the genres and time periods, let alone have an understanding of how they flow together, let alone have a grasp on the many prominent literary theories about all these works. And those things are all suitable for a beginning student to know. As you go up the more potential things there are for you to know, so the tests don't get any easier. Which is fine, as long as you don't expect people to know 90% of it
I think it becomes confusing here because we mix the idea that a grade tests your knowledge of what the class taught, and your position as "average" "above average" "excellent" So in many undergraduate programs you are expected to maintain a B average in your major. So EVERYONE in that third year class is probably trying to get a B, making B the average, not a C. This is extended to Graduate school where I, like Linds, am expected to get a B or better in all my classes because I am here to excel. Or I am here because I am above average, so an "average" grade is not good enough (or something). So the average is now probably a B+ meaning that I am no less average within my program, there is just less room for error. Many of the professors additionally make it quite difficult to get a true A on an assignment, because this is Grad school, so of course things are graded tougher.