The theory is that low-SES students will perform better in these school districts. Educated parents are supposed to value education more highly and care about the education their children are receiving. Apparently, these high-SES districts attract better teachers, have better students with better motivation, have more resources, can pay more attention to the small number of low-SES students, and the like. The children of these highly educated parents are supposed to value their education more highly and, as a result, will perform better. In theory, low-SES students should perform better when in classrooms with these children of the highly educated.
Let's see if the data supports this theory.
The graph compares student achievement (11th grade combined math and reading) with the percentage of adults with bachelor degrees residing in the school district. There are two populations being compared. The pink squares represent all students. The blue diamonds represent economically disadvantaged students (those qualifying for free or reduced lunch). I added trend lines for both populations and also indicated the mean score of all students (the horizontal red line. Mean = 60.7) .
Here's the regression results for all students:
- R = 0.56 (there is a medium association between parental education (of the community) and the performance of all students)
- R2 = 0.312 (there is a medium fit between the data)
- P = 3.77729 x 10-42 (the results are statistically significant)
Here's the regression results for low-SES students:
- R = 0.22 (there is a small association between parental education (of the community) and the performance of low-SES students)
- R2 = 0.048 (there is a low poor between the data)
- P = 0.000003 (the results are statistically significant)
(The correlation between high-school diplomas and student achievement was similar.)
We see that as parental education increases so does student (all) scores. There is a medium sized correlation and fit between the data. This correlation is well known.
Things start falling apart, however, when we look at the performance of low-SES students. We should expect to see a lower correlation because we've restricted the range of students. Both the correlation and data fit for low-SES students is low. The trend is not reliable given the low data fit. I've left it in for reference purposes. Whatever is causing the increase in student (all) scores seems to be missing from the low-SES student scores. The magic aura of the kids with highly educated parents does not seem to be rubbing off as well as some have predicted. Few of school districts have low-SES scores above the mean for all students.
To the extent that low-SES test scores are slightly higher in school districts with high percentages of highly educated parents, this is most likely attributable to rising SES status of the low-SES students. We know that SES is positively associated with student performance. We also know that the variance in family income for students eligible for free or reduced lunches is wide and includes about 40% of all students, i.e., most students to the left of the mean.
The take away is that just because the correlation between parental education and total student performance is midsized, does not mean that the correlation between low-SES student performance and parental education is also midsized. It's much lower than that. And the student achievement gains we should expect to see by placing low-SES students in higher-SES school districts (as a function of parental education) will likely be low to non-existent. In any event, we should not expect those gains to pull low-SES student achievement up to the mean performance of all children based on this data.