I don't think those graphs are indicating what you think they are. Since the overwhelming majority of Asian students come from two-parent households even low-income Asian students have a greater advantage over all other ethnic groups. The same could be said for the correlation between parental education level and the child's future academic performance.

Asian Americans have the highest educational performance in the United States. Just over 51% of Asian Americans have a four year degree as opposed to 30% of all Americans and even less amongst African Americans. So, even a poorer Asian American student has advantages over a slightly "wealthier" black student.

No matter how you slice the data it shows the exact same thing: INCOME is the greatest single predictor of academic achievement. Asian Americans earn almost double the median income in the US. So if you're born Asian in the United States you are more likely to:

A. Live in a two parent household.

B. Have at least one parent with a four-year degree or higher.

C. Have a higher family income than ⅔'s of African Americans.

D. Live in school district with higher performing schools.

When coupled together of course Asian American students perform better academically than African Americans. Their average higher incomes almost guarantee that.