We should be concerned with the gap as much as or more than the level of proficiency. If we are only concerned with the level of proficiency, the strongest and most privileged students will excel, while other students (mostly minority students) will fall behind. As a whole, this is bad for society because a gap will cause minority students to be discouraged and drop out of school.
Yes, as a nation, we should be concerned with the gap in proficiency between black and white students as it implicates many things about our culture, not the least of which is that white students are likely given better opportunities than are black students. We must work to make sure these opportunities are the same and not based upon race.