SAT scores and Income
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Just found these data for NC: The fraction of students taking free or reduced lunches (a measure of poverty) and the composite performance score for 2,535 schools in NC. These data are pruned from larger sets to make sure both items exist for each school.
A particularly large argument has erupted in Wake County with the election of a new school board determined to eliminate busing for diversity. Some have made comparisons with Charlotte-Mecklenburg schools, so here’s a plot pulling out that data:
[click on the plot for a larger image] Clearly, the C-M school district has more economically challenged school districts than Wake County. Why? Below I show data indicating that Wake County has the second-highest per capita income in the state. Ahhh, how about that: I just found out that Mecklenburg County (it holds Charlotte) has the highest per capita income. So, the question might be, has Wake County’s busing reduced the high poverty schools and increased performance? Wake’s average performance is 77.9 whereas Mecklenburg’s is 74.4, giving Wake about a 5% higher score despite having a lower income. Is busing for diversity increasing the scores of students whose neighborhood school would have a greater concentration of lower income students and lower performances? I don’t know. Would Mecklenburg do better by transferring the students from schools with, say, more than 60% free lunches to higher income schools? I don’t know. Downey (2007) provides results on segregation and minority income for major U.S. cities. Both Raleigh and Charlotte have B/W income ratios of 0.591 (blacks have 59.1% of the white population’s income), but the segregation in Charlotte is greater: 55.2% of Charlotte’s black population would have to move to reach a “uniformly mixed population”, whereas only 46.2% of Raleigh’s black population would have to do so (apparently that’s a standard measure for segregation).
So, both metropolitan areas have similar economic conditions for blacks, Charlotte is more segregated, and Wake has bused for diversity. Presumably, both factors could be responsible for Wake’s historically better performance. I guess we’ll have to wait and see how the new Wake school board’s experiment plays out. It would be nice to see the data from the studies they have that form the basis of their changes.
Here’s the spreadsheet with NC schools with information on free lunch and performance. I’ve pruned some data where one or the other wasn’t available: combined
School performance decreases with this particular measure of low income. Here are data from three counties around Durham:
All three counties show similar trends with low income, though Wake County seems a little higher (I didn’t do the stats yet, but the points sure look higher). That is until the new Wake County School Board gets done doing what they’re doing with their schools.
Just to be clear, higher family income promotes better scores on standardized tests. Here I show data from North Carolina counties, plotting SAT scores versus family income, measured over the 100 counties:
Overall, a pretty dramatic dependence. These data don’t really belong in “environmental inequity”, in the sense that family income doesn’t fall under what I’m thinking of as the natural environment. However, as I’ve posted under the Durham category, family income also influences tree canopy levels. Wake County prides itself on higher education scores, yet that pride should be tempered by acknowledging it’s level of wealth.
It’s not just a matter of spending money on students. This plot below shows SAT scores varying as functions of federal, state, and local expenditures per pupil. All of the monies add up to essentially equivalent total EPPs, with state and federal sources making up for lower local sources, but it’s really the above plot — family income — that seems to determine student achievement.
The data was/is available on the web, but I’m happy to provide it to you.
Here are the SAT scores across school systems in NC, 2004-6. 2006Table6
(I’m looking in my files for my county income source.)
I’d like to collect more examples of income and academic performance: If you have one or more, please send me a comment with a link to the data or publication. I’ll take a look, plot it up, and post it here.