Wouldn't any attempt to use income level as a proxy for race be vulnerable to accusations of disparate impact? As I understand it, a policy or program which is not explicitly biased can still be held to be impermissable if an analysis shows that it produces biased results.

This is the line of reasoning used to argue that colleges should not use the SAT for admissions, or to prohibit redlining by banks. I would expect segregationists to cash their winnings from this round and then start a new round of lawsuits against any replacement policy on the grounds of disparate impact.

We should bus white kids past their neighborhood schools to another school in the name of racial balancing? That's what the government was doing to Brown

Assigning student to schools based on where they live produces hugely disparate results. In fact this often leads to segregated schools.

I think any of the income based plans would produce less a less disparate outcome then the neighborhood based plans which they are replacing (after all that's their point).

I agree with you that those whose don't want poor people in their schools will make the argument you outline, but I think that you overestimate the power of this argument.

In short, no. Disparate impact applies to employment decisions under Title VII of the Civil Rights Act. Instead, the Courts use the 14th Amendment's Equal Protection Clause to evaluate discrimination in schools. Under the Equal Protection Clause, classifications based on race are subject to "strict scrutiny" a much higher burden than the "rational basis" used to evaluate classifications based on economic basis. Thus, the classification would likely be constitutional.

to ask is whether skin color has more power than culture..

I think the answer is no and offer Elvis Presley as a perfect example of black culture in white skin.

The new decision leans toward eliminating the biases unitentionally built into the original decision in brown. Income level is probably the only practical handle to that gradient..not a pefect handle..but certainly the more effective one.