A lot of this has to do with parental expectations and even the demographics and school background.

Where I went to high school, everything was ultra-competitive, and the standard "quantitative" measures of ability were sky-high. My SAT score of 2170 (out or 2400) was on the low-end compared to most of my colleagues and my SAT II scores were slightly below the "smart kid average" as well. It doesn't mean that the whole school was this way, but a large number of kids and their parents expected As and nothing less.

At the University, everything is a bit different, because the student body is widely dispersed and much larger. I'm not a straight A student, and nor do I expect myself to be. I put in an honest effort, and whatever grade I receive is what I receive, end of story. Given the cut-throat nature of my high school, the academic transition was well.......easy. Then again, I'm not that "in tune" with what kids might expect in college, so it's hard to say. I do think that a B-/B/B+ is expected for kids who put in a genuine effort.