For the same reason there are so few poor whites in STEM. America's dysfunctional education funding. Make education funding federal, and have a nationwide push to have small classes and well funded schools for everybody, and this would be fixed in 10 years. As it is, rich districts pay more taxes and get better schools. Funny that.
Seems like there are 2 problems with this. First is that the federal government doesn't have the legal standing to take over the education system. I believe it would require a constitutional amendment to allow it and I don't think they'd get that passed. Secondly, I'm not sure it is such a great idea. Currently federal level education direction comes from the teachers union and you can see the fruits of its labors in…
Nor does the federal government have to take over the education system to achieve this, it just has to guarantee equal funding for all students. Or the US can continue to set poor whites against poor blacks as it has now for centuries, and watch itself become increasingly uncompetitive with any country that makes a commitment to equal educational standards for all. "This used to be the greatest country in the world", etc.