Mapping State Proficiency Standards Onto NAEP Scales: Results from the 2013 NAEP Reading and Mathematics Assessments
http://nces.ed.gov/nationsreportcard/subject/publications/studies/pdf/2015046.pdf
Differing state standards make it difficult to measure student achievement at the national level. This report presents the results of a method for blending state standards with those of the National Assessment of Educational Progress for measuring reading and math proficiency. From the National Center for Education Statistics