Today’s The Answer Sheet features a column by Matthew Di Carlo of the Shanker Institute wherein he compares the NAEP math and reading scores of states “with binding teacher contracts” to states without. He finds the contract states to have scores an average of 2.65 points higher.
He concludes this way:
If anything, it seems that the presence of teacher contracts in a state has a positive effect on achievement.
Now, some may object to this conclusion. They might argue that I can’t possibly say that teacher contracts alone caused the higher scores in these states. They might say that there are dozens of other observed and unobserved factors that influence achievement, such as state laws, lack of resources, income, parents’ education, and curriculum, and that these factors are responsible for the lower scores in the 10 non-contract states.
My response: Exactly.
Di Carlo isn’t comfortable claiming flat out that collective bargaining increases student test scores, but emphasizes that the opposite argument – the absence of teacher contracts would benefit test scores – lacks evidence. In his follow-up blog post, Di Carlo delves deeper into the numbers, and finds:
Finally, in all four models, the association between scores and whether or not states have binding contracts is not statistically significant at any conventional level (even at the 90% confidence level). So, while this analysis is far from conclusive, I certainly find no evidence that teacher union contracts are the among the biggest reasons why achievement is low, as Davis Guggenheim and countless others imply (see here and here for more thorough analyses, which actually show small positive benefits of unions).
It’s going to be difficult for some to resist the temptation to argue about what effect, if any, teacher contracts have on student test scores from state to state, but it entirely misses the salient point that the purpose of teacher contracts is not, and never has been, to increase student test scores. In states with collective bargaining, contracts define the salaries, benefits and working conditions of public education employees. Since compensation accounts for upwards of 80% of all public school expenditures, we might learn something about the “real effect of teachers’ union contracts” if we compare per-pupil spending in states with binding teacher contracts to states without. Here, I use U.S. Census Bureau figures for 2007-08:
Average per-pupil spending in AL, AR, AZ, GA, LA, MS, NC, SC, TX, and VA – $8,904
Average per-pupil spending in the other 40 states and DC – $10,745
Stating there is no significant difference between bargaining and non-bargaining states when it comes to student achievement is not a winning argument for unions. We pay a 20.7% premium to have unions. Isn’t the onus on them to demonstrate their worth to students, parents and taxpayers?