You're almost directly channeling Dr. King, in fact. His speech of March 25th 1965 contains much the same.
Such schools don't even make a specious claim of "separate but equal" - they are specifically and purposefully "drawing off the cream of the crop" to assure that the students that are already advantaged through income disparity, parental education or simple genetics will be placed in a superior learning environment.
In order for the above paragraph to be true, it should be obvious that such systems ensure that those who need the most educational intervention are granted the least. That, to me, is the very heart and soul of structural racism, right there, that is what created and perpetuates the issues of this thread.
Statistically, if an American child has no library in their home, that makes it far more likely that there is no library in their school. Uneducated parents, increasingly left behind by an increasingly automated labor market, cannot by themselves make up for the lack of education that test-in school systems are testing for. Such parents are mostly white, it is true, but the population denied optimal educational opportunties is disproportionately composed of people of color, by orders of magnitude. It is this disparity that makes it possible for police and bankers to use skin color as a proxy for income and social status levels, which is again the expression of structural racism.
It all starts with the schools. Magnets and charters and private schools are the driving engine of racial injustice.
The reason it works is simple; every parent wants their child to have the best education they can get. So, as long as there is a way to get your child into a better school, nearly everyone who can, will. And they'll justify it various ways, and ignore the fact that any unequal educational system will always victimize the already economically disadvantaged.