It found that the bottom 10 percent had gained far more than the national average since 2000 in math and reading, more than a full grade level in math. (educationnext.org)
Using the National Assessment of Education Progress (NAEP) as our measure, we found some states had raised the achievement of economically disadvantaged students the equivalent of a full grade level or more in just eight years, 2003 - 2008 — this at grades four and eight and in reading and math. (educationnext.org)
Applying that here, scores for most groups of students have improved by roughly a full grade level over the last 15 years or so. (educationnext.org)