In a previous post, I presented a simple tabulation of NAEP scores by whether or not states had binding teacher contracts. The averages indicate that states without such contracts (which are therefore free of many of the “ill effects” of teachers’ unions) are among the lowest performers in the nation on all four NAEP exams.
The post was largely a response to the constant comparisons of U.S. test scores with those of other nations (usually in the form of rankings), which make absolutely no reference to critical cross-national differences, most notably in terms of poverty/inequality (nor to the methodological issues surrounding test score comparisons). Using the same standard by which these comparisons show poor U.S. performance versus other nations, I “proved” that teacher contracts have a positive effect on states’ NAEP scores.
As I indicated at the end of that post, however, the picture is of course far more complicated. Dozens of factors – many of them unmeasurable – influence test scores, and simple averages mask them all. Still, given the fact that NAEP is arguably the best exam in the U.S. – and is the only one administered to a representative sample of all students across all states (without the selection bias of the SAT/ACT/AP) – it is worth revisiting this issue briefly, using tools that are a bit more sophisticated. If teachers’ contracts are to blame for low performance in the U.S., then when we control for core student characteristics, we should find that the contracts’ presence is associated with lower performance. Let’s take a quick look.