Let’s get one thing straight: As I’ve noted on numerous occasions, you can’t look just at National Assessment of Educational Progress (NAEP) results – especially only between two years – and attribute gains or losses to specific laws or programs. There are simply too many variables at play in education – federal laws, state laws, school choice, child nutrition, teacher quality, parents’ attitudes, the weather – to confidently assert that any one is responsible for changing scores. Indeed, it is possible that nothing government has done has had any effect, and every trend just reflects changing attitudes toward education among students themselves.

And yet, some reporters identify something akin to a god variable anyway, as the Associated Press did in its coverage of the new NAEP long-term-trends report:

The biggest gains came from low-achieving students. That is probably not an accident — the federal No Child Left Behind law and similar state laws have focused on improving the performance of minority and poor children, who struggle the most.

Now, there are a lot of problems with this statement, including that several of the lowest-achieving percentiles by age and subject saw no statistically significant changes in scores between 2004 and 2008; many groups had periods of faster gains before NCLB (though we don’t even have clear before and after-NCLB data points); and NAEP offers no income-based score breakdowns, only the proxy of parents’ education – and that just for 13 and 17-year-olds in mathematics. But the biggest problem is that, all of these factual problems aside, there is no way to ascribe score changes to specific laws or government policies. The data just aren’t there.

Fortunately, most of the coverage of the NAEP report has been pretty reasonable, including from the Washington Post and New York Times. But the AP reaches a lot of people, and that means many Americans are going to get “news” about the latest NAEP findings that is little more than unsupportable conjecture.