This reminds me of the test called "matura" that we have to take in Poland when we finish high school. I believe in English it could be called "secondary school certificate" or "high-school certificate" and you need to pass it if you want to educate further (go to college/university). When it comes to math, the results look like this:
But when it comes to humanities, the results are weird: 
Why? Because teachers that were verifying tests were able to cheat a little and help students that "almost" passed and bump their score by a few points, so they will be above the point required to pass the test :) You can not do that with math tests where it is clear that you're either right or wrong, but in humanities where you have to write some kind of essay or things like that it is more subjective.
RE: Exploring incentives: An Investigation of thousands of logs reveals exactly what most Actifitters aim for