Example of how SAT can be biased rests in the accuracy of the test materials. For example I did well in math and science but failed history because I disagreed with the SAT on History as it is mostly from an inaccurate & WHITE perspective.
Not to mention that, now that Loren in the other thread brought up Baseball questions, there was at least one or two baseball questions on the SAT in the math portion when I took it. In fact, sports seems to be a very common basis for word problems in math, owing to the fact that numbers feature so heavily in player statistics.
With regards to reading comprehension, similarly, there are vast differences between certain cultural groups of the United States, and various forms of English to comprehend in the first place. English Professors in general tend to be pretty culturally biased when it comes to an idea of which "English" is the correct "English". In fact a lot of the posters posting in this thread seem to have some rather concrete ideas about what constitutes "correct" English which I have tried to disabuse them of on various occasions, and here they are expressing Incredulity that tests could potentially fail to reflect individual ability.
Really, all those tests should be good for is to discern over/under on "has at least the bare minimum of learning ability". "What you know" is a bad proxy for how capable you are of "ability to know". It's easy enough to catch up with an ability to know, but it's hard to continue learning more regardless of what you know if you lack the ability to keep learning.
This is, ultimately, what admissions should be focused on.
I would, were I considering admissions of some sort, be more intent on admitting the student from a shitty highschool with a moderately high SAT score than I would be on admitting a student from a great school with a slightly higher SAT score. This is because one student demonstrates an above average ability to learn, and the other has demonstrated mediocrity, even though the mediocre student still scored higher.
Further, as long as it includes "history of white people as taught by white people", it will continue to transmit such blatant biases as you point out