With respect to GRE math, most graduate programs in mathematics require the GRE subject test in math, which is much more challenging and covers all of the material one would go through for a BS in math (calculus, topology, real analysis, set theory...). I'm not sure what other subject exams are given, but it might be that the GRE general exam is used to show competence, and that the subject exam is to differentiate ability.

I'm also a bit dismayed that the education students score so low and are assessing children on abilities in these areas...