It's a general rule, I've observed, that you can't discriminate between levels too far above your own.

Although I agree with this in general, it seems that there are a few specific counterexamples. For example, it seems that people with very low ability in sports actually can discriminate ability from the local high school level to the international stage.

Do other people agree? If so, what do you propose distinguishes between intelligence/mathematical ability and athletic ability?