On the suspicion that the branches might correspond to SES levels, we constructed a crude SES partition based on average home values. Figure 3 shows the result of this partition for middle-income performance at the satisfactory level. Most of the scatter is gone. Trends are more evident. Racial integration raises black performance and lowers white .
Regression supplies the answer.
We fit pass rates to a linear model, using black eighth-grade percentage and average neighborhood home value as independent variables. The results are summarized in Table 2.