I would posit that it is the students that are holding themselves back. Further, I would add that it is only one or two categories of minorities, not the full spectrum, i.e. Asian (Oriental, Indian, etc.) minorities excel at mathematics. The delta is in the cultural acceptance of self-discipline when it comes to mathematics, engineering and the sciences.
Their DNA is not pre-disposed to reject higher learning.
I totally agree. But the narrative for the last fifty years is that schools fail the students. Fifty years ago when I was in school and I did poorly in some classes (and I did poorly in a number of classes), the school was not blamed. The onus was put on me for not studying hard enough and for not paying attention during class. For which I plead guilty as charged.
But since then, both liberals and conservatives have seen fit to blame the schools for poor student scholastic performance. I doubt the schools are at fault. I've read too many stories of Asian immigrants doing very well at many of these "poor" schools to believe it's the schools.
When a student doesn't do well in school, 90% of the time it's the student and his family who are at fault.