What has NCLB done?

While Massachusetts students top the nation in math scores in the National Assessment of Educational Progress, the New York Times points out the larger picture:

The latest results on the most important nationwide math test show that student achievement grew faster during the years before the Bush-era No Child Left Behind law, when states were dominant in education policy, than over the years since, when the federal law has become a powerful force in classrooms.

There's also a graph.

While David Driscoll (and when did he become the chairman of the National Assessment Governing Board?) cites the lack of knowledge and preparation in math by teachers, that doesn't explain why we were doing better before NCLB.