[Ghoulish Delight]

That's one theory. Another one has shown that standardized tests, especially in things like vocabulary and reading comprehension, are biased based on socio-economic lines. They make certain assumptions about "common knowledge" that is only common if you're above a certain economic class. Assumptions about what a home looks like, who cooks meals, who takes care of kids, etc. It's subtle, but it's been shown to make a difference.

Never mind that these, by necessity, are multiple choice tests. There are techniques for taking these which can guarantee better scores, without necessiraly better knowledge. I'm a master of multiple choice tests, no matter how clever the test maker gets. They are good to a point, but are severely lacking.