Here the overarching problem with these statements. They are trying to pass judgment on a race based on certain statistics about them. Is it racist to say that black students on average score lower on the SATs? No, it is a statistical fact. Is it racist to proclaim these students as stupid because of that? Yes, extremely, because you are judging their intelligence base on race without understanding why that statistic might be true.
Instead of being so heavily concerned with what you "can" and "can not" say without being racist, its important to focus on why these statistics do exist and understand why they are true.
Your statement implies that the student is stupid because they are black. That is racist and strictly false. So why do these students score lower? Probably due the incredibly high level of institutionalized racism that they experience every day of their life.
We need to work towards building a better society together, and eliminating societal constraints based on characteristics beyond their control characteristics. By focusing on how you can't say racists things (and if you didn't know it would be racist, then not bothering to understand why), and how that is unfair to you takes focus away from the real issues. Black students are scoring lower on the SATs, and its because as a society, we have institutionalized racism towards them. That is the great injustice here, not the lose of anyone's right to remain ignorant.
"Probably due to the incredibly high level of institutionalized racism that they experience every day of their life."
I completely agree. I have seen first hand cops being completely racist to minorities. And there are numerous cases of African Americans having their race being a factor in getting a job (http://www.chicagobooth.edu/magazine/sum_fall03/bertrand.pdf). There are a million other difficulties they face. I wan't to do everything possible to remove those barriers.
I'm not implying people are stupid because they are black. That is just something you are picking up from nothing. What I said is the English version of:
P(scores is in bottom decile | student is Black) > P(score is in bottom decile | student is White).
Is there a difference between someone being "stupid" and someone scoring very low on a g-loaded intelligence test? The first definition of stupid on Google is "lacking intelligence". Is it wrong to say someone whose intelligence test scores are very low is stupid? I'd probably say test scores <25 percentile = stupid, between 25 percentile - 75 percentile average, >75 percentile smart. (Obviously you have to make sure the test isn't biased which is why I originally mentioned math).
If I changed from saying scored bad on the SAT to being illiterate as an adult does that make my statement any better. It seems like no one can say someone who is illiterate isn't stupid.
My point isn't to worry about what you can and can not say without being racist. I already know that judging individuals based on their race is wrong. I'm trying to use an analogy to say that if we can all agree that saying one thing is wrong, saying another thing about judging white people when it is also a generalization/stereotype is equally wrong.
That doesn't judge their character but you still can't go shouting it whenever anyone brings up black people.