In the U.S., there is no recent database of district-level test scores that is comparable across states. We construct and evaluate such a database for years 2009-2013 to support large-scale educational research. First, we derive transformations that link each state test score scale to the scale of the National Assessment of Educational Progress (NAEP). Next, we apply these transformations to a unique nationwide database of district-level means and standard deviations, obtaining estimates of each districts’ test score distribution expressed on the NAEP measurement scale.