For years now, America's elementary and middle school students have been showing steady gains in test scores on the National Assessment of Educational Progress. This has happened even as the underlying demographics of the public school population have shifted to include a larger mix of poor kids, nonwhites, and kids whose parents don't speak English.
High school test scores, by contrast, stagnated during the early years of this process. But optimists hoped and assumed that when the higher-scoring elementary school kids got older and moved into the high school population, we would start seeing results. It's now become clear that's not happening. On the contrary, even as America's ninth-graders keep doing better and better, its 12th-graders are doing worse and worse.
This has naturally produced a lot of consternation in education circles, but one approach has been to try to explain away the declining trend as a result of demographic shifts or some other statistical illusion. That chart comes from a new paper by Kristin Blagg and Matt Chingos of the Urban Institute, who say that, on the contrary, as best we can tell from the data that exists (they explain some limitation) the various illusion hypotheses are wrong. The progress that is being made with 9-year-olds and 13-year-olds is fading out and not producing results for high school seniors.
How to use this chart to bolster your preexisting views
This strong divergence roughly coincides with a period during which the federal government has been pushing an agenda of "education reform," and conveniently this data can be spun to support either side of the controversy around reform.
If you think education reform is bad: You want to say this data proves that despite the superficial appearance of success with younger kids, the reform agenda is actually doing nothing to help American teenagers graduate ready to succeed at work or in college. We've put teachers through a lot of changes they don't like, made kids sit through tons of tests, and even closed schools, and it's all accomplished nothing.
If you think education reform is good: You want to say that most of the controversial measures around testing and accountability only applied to elementary and middle school, with high school accountability measures focused on graduation rates — which have gone up. The entire reform agenda is based around the philosophy that what gets measured gets improved, and what we see here is the things that were measured — math and reading for younger kids, graduation for teenagers — have in fact improved.