Interestingly, this is right on par with the national average of 82% white primary and secondary school teachers, and the number has barely changed at all across the country in 15 years despite massive demographic change and tons of efforts to change it.

The link from Harvard you post below attributes it to attrition - that people have raised recruitment of teachers of color, but it has failed to actually diversify the workforce, because teachers of color don't stay in the profession. The reason put forth by the article that they don't stay in the profession is that they disproportionately want to teach in schools with lots of students of color, which are, disproportionately, very negative working environments that drive them to quit.

So the question to address the issue would be, what can we do to make low-income schools more attractive working environments, and what could we do to target retention of committed, long-term teachers.

It's a whole separate issue, but obviously Teach for America has been shown to be an utter failure at this point at building the teaching workforce and helping low-income schools. We can all agree on that, right?