More on NAEP Poverty Gaps & Why State Comparisons Don’t Work
This post is a follow-up to a recent post on how income distributions differ across states and how those income distributions thwart our ability to make reasonable comparisons across states in the size of achievement gaps in relation to low-income status. To review (so you don’t have to necessarily go back and read the other post, which is here):
Here’s the basic framing adopted by most who report on this stuff:
Non-Poor Child Test Score – Poor Child Test Score = Poverty Achievement Gap
Non-Poor Child in State A = Non-Poor Child in State B
Poor Child in State A = Poor Child in State B
These conditions have to be met for there to be any validity to rankings of achievement gaps.
Now, here’s the problem.
Poor = child from family falling below 185% income level relative to income cut point for poverty
Therefore, the measurement of an achievement gap between “poor” and “non-poor” is:
Average NAEP of children above 185% poverty threshold – Average NAEP of children below 185% poverty