Recently, San Diego Unified bookended the school year with good news: District officials predict a graduation rate of 92 percent  – an all-time high. Even more impressive, San Diego Unified students have done it under more rigorous graduation requirements.
An official tally won’t be available until late next school year, but districts officials expect the rates to hold strong.
San Diego Unified isn’t the only California district making gains. Last month, the California Department of Education announced that for the sixth straight year , both graduation and dropout rates improved statewide. The persistent achievement gap between white students, Latino and black student students has slightly narrowed.
Gov. Jerry Brown credited the improvements, in part, to the increased funding schools have seen since 2013.
But the high graduation rates don’t explain why, after decades of talking about the achievement gap, California hasn’t made more progress.
And that ties into a question sent in by one of our readers.
Question: How does the achievement gap in California compare to the gap in other states? – Matt Patterson, VOSD reader
This is a great question. But it turns out that it’s an especially tricky one to answer.
The National Assessment of Educational Progress collects and reports how public school students are doing on a common test, across states. If you look at the results of those tests , you’ll see that between 2003 and 2015, California consistently fell below the national average in reading and math when it came to the percentage of students who scored proficient.
The racial achievement gap varies, depending on which age group, and which set of test results you’re looking at. But in 2015, the gap in fourth grade reading scores  between white and black students, as well as the gap between white and Hispanic students, was slightly worse than the national average.
That gives us some indication of how California students stack up, but it’s not a clean comparison. States have different thresholds for what they consider “proficient.” That means a student who tested “proficient” in California may have a significantly different score than a student who scored “proficient” in New York.
This is where Sean Reardon, a professor of poverty and inequality in education at Stanford University, comes in.
Reardon and a team of graduate students built a database containing  the results over 200 million assessments – that is, every test taken by middle and elementary students in the United States, between spring 2009 and spring 2013.
Then, they developed a set of statistical methods for tying NAEP results to the results of other tests students took in school. To check their work, researchers made predictions, based on past performance, for how well students would score in certain parts of the country. Those predictions came true and Reardon knew he was on the right track
When researchers took the work to scale, they discovered that racial achievement gaps exist in nearly every school district across the nation.  Even more remarkable, they found that many of the districts we might think of as affluent or well-resourced had some of the starkest disparities.
Berkeley, Calif., for example, has one of the worst gaps in the country. (Which is especially surprising, given that Berkeley has been held up as a model for racial integration). Other university cities, like Chapel Hill, N.C., and Evanston, Ill., home of Northwestern, also topped the list.
Only one urban school district showed no significant gap: Detroit. And that’s not because Detroit is a poster child for school equality, Reardon told VOSD. It’s because students across all ethnicities are doing poorly in Detroit, so nobody really wins out.
Reardon has a theory about why achievement gaps persist in prosperous school districts.
“In the most advantaged places, you have this increased competition and focus on school success as important for kids — a hyper-achievement orientation in those places,” Reardon told EdWeek. “And in places where competition is high, resources matter even more than they do in places where you don’t have that sort of achievement anxiety.”
Locally, we see this conversation take place over school funding. Two years ago, we published a series of reports on school foundations , which are usually parent-run nonprofits that raise money to supplement funding for their schools.
In 2012, school foundations across San Diego Unified raised about $6.5 million , a lot of which stayed at affluent schools in La Jolla and Scripps Ranch. Schools in low-income communities raised a fraction of that, if they raised anything at all.
Several parents I spoke to in La Jolla, though, were quick to point out that schools with high concentrations of low-income students usually get more resources and funding from the state and federal governments.
These parents weren’t wrong, but the argument is sort of a red-herring. Schools have a lot more discretion as to how they spend unrestricted, foundation-raised money. (And if we’re just looking at funding, it’s the schools in middle-class neighborhoods that often get the least .)
The point is, tension and anxiety play out, to varying degrees, every year.
In a video posted by EdWeek, Reardon says his purpose for studying achievement gaps was to gain a better understanding of how much we can expect to boost educational equality with improvements to the school system alone – through teaching and learning – and the degree to which we might have to look outside the school system if we want to make lasting improvements.
Put more simply, he wanted to see the degree to which educational inequality is fixable, and the degree to which it’s structural – that is, based on factors like poverty or neighborhood conditions.
Reardon said he has more work to do before he can answer the question completely, but in short, he’s convinced that what happens in the home is at least as important as what happens in the classroom.
In other words, both things matter. Here he is in a 2012 interview with Edsource :
“There are two sides to that argument. You can say schools can sort of do it on their own, and let’s not call attention to poverty. Or you could say schools can’t do anything because there is so much inequality outside school, and we are fooling ourselves if we think we can fix this without fixing the bigger issue of structural inequality,” Reardon said.
“Well, schools can do something, so it is not accurate to say schools can’t do anything. The right answer is that both schools and larger social inequalities play a big role and we are not going to make real progress without working on both fronts at once.”