Teachers Unions, ACT/SAT, and Student Performance: Is Wisconsin Out-Ranking the Non-Union States?
As I posted yesterday, the tweets going around comparing Wisconsin’s SAT/ACT scores to five states where teachers have no right to unionize are based on bad data — it’s not true that Wisconsin’s SAT/ACT ranking is second in the nation, and that Texas, Virginia, Georgia, North Carolina, and South Carolina are all clustered at the bottom of the pile. The chart that says otherwise is based on outdated statistics and improper statistical analysis.
So what’s the truth? What would good data tell us about this question?
Well, it turns out that that’s kind of complicated.
It’s hard to measure SAT/ACT performance, because different numbers of students take the tests in every state, and comparing the strongest students from one state with a much bigger sample from another doesn’t tell us much that’s interesting. A 2000 study in the Harvard Educational Review, in fact, found that 85% of the difference in states’ performance on those tests is due to variation in participation rates.
Having said that, though, it’s clear from the numbers in my last post that once you’ve controlled for participation Wisconsin remains near the top of the country on SAT/ACT scores, Virginia is near the middle, and the rest of
