Allan Bevere has some interesting observations about grade expectations by students:
When I was in college and graduate school many years ago, most students, I think, had no assumptions about what grade they deserved on an assignment for a class. There were exceptions to this, of course, but when I received a B on a research paper and was told that the paper was good, I assumed that the professor believed, for various reasons, that it was indeed a good piece of work and not an excellent finished product. The professor did not have to justify why I did not receive and A. After all, I was the student, the learner. I was being trained in the subject of theology, I did not have the expertise my professor had.
That is no longer the case. Today professors have to justify why an assignment did not receive an A. The assumption from many students that the A is the norm and anything less needs an explanation.
On more than a few occasions I have had emails from students after not receiving an A for the course wondering why they received a B (or less) since they did turn in all the assignments. Apparently, the quality of the work for some is not the determining factor in the final grade; simply turning in the assignments is sufficient.
You can read the whole thing here.