The No Child Left Behind Act (NCLB) has been criticized for encouraging schools to neglect students whose performance exceeds the proficiency threshold or lies so far below it that there is no reasonable prospect of closing the gap during the current year.

This study examines this hypothesis using longitudinal data from 2002–03 through 2005–06, comparing the mathematics achievement distribution in a grade before and after it became a high-stakes grade.

The authors find in general no evidence that gains were concentrated on students near the proficiency standard at the expense of students scoring much lower.