Why you can’t compare simple achievement gaps across states! So don’t!

School Finance 101

Consider this post the second in my series of basic data issues in education policy analysis.

This is a topic on which I’ve written numerous previous posts. In most previous posts I’ve focused specifically on the issue of problems with poverty measurement across contexts and how those problems lead to common misinterpretations of achievement gaps. For example, if we simply determine achievement gaps by taking the average test scores of children above and below some arbitrary income threshold, like those qualifying or not for the federally subsidized school lunch program, any comparisons we make across states will be severely compromised by the fact that a) the income threshold we use may provide very different quality of life from Texas to New Jersey and b) the average incomes and quality of life of those above that threshold versus those below it may be totally different in New Jersey than in…

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