Is Mississippi Proficient in Math?

In Time Magazine, Walter Isaacson makes a compelling argument for national standards in education. Here’s a tease:

National standards have long been the third rail of education politics. The right chokes on the word national, with its implication that the feds will trample on the states' traditional authority over public schools. And the left chokes on the word standards, with the intimations of assessments and testing that accompany it. The result is a K-12 education system in the U.S. that is burdened by an incoherent jumble of state and local curriculum standards, assessment tools, tests, texts and teaching materials. Even worse, many states have bumbled into a race to the bottom as they define their local standards downward in order to pretend to satisfy federal demands by showing that their students are proficient.
It's hard to argue with his premise: that without national standards, states play a statistical game of dumbing down curricula to escape the sanctions of No Child Left Behind. Isaacson gives us a case study of Mississippi where the state claims that 89% of their fourth-grade kids are proficient in reading. Hey! That’s the best in the whole country! Something in the river? Nah, the national test given periodically by the National Assessment of Educational Progress shows that only 18% of fourth-grade Mississippians are meeting benchmarks and, in fact, they rank as the worst in the country.