The Pierre Capital Journal makes available this fun map of South Dakota school districts and their average teacher pay and ACT scores:
Naturally, that map got me wondering: do we find any correlation between the two figures featured here, teacher pay and ACT scores?
I rush to the state Department of Education's Statistical Digest, spreadsheetify the 2013 data, and uncover the following correlations for schools with ten or more kids taking the ACT in 2013:
- Average Teacher Salary to ACT Composite Score: 0.1037
- ATS–ACT English: 0.1839
- ATS–ACT Reading: 0.1151
- ATS–ACT Science: 0.0431
- ATS–ACT Math: 0.0268
- ATS–# students taking ACT: 0.3713
- ATS–high school graduation rate: –0.2526
The ACT numbers suggest a faint association between higher teacher pay and student scores. But the only correlation with statistical significance I feel comfortable citing is the correlations to ACT reading scores, and even that number, 0.18, is so practically small that, even if it hints at some boost kids get in class from our paying their teachers more, that boost could easily be overwhelmed by a grouchy principal or one mild flu outbreak.
The last two correlations are somewhat more significant, suggesting that higher teacher pay aligns with more students taking the ACT but more students struggling to graduate. Those two correlations are still smaller than my "Holy cow!" threshold. But even if you see something worth reading into a –0.25 or +0.37 correlation, note that those two numbers on teacher pay may really just be a back-door way of reminding us that bigger school districts have slightly lower graduation rates (correlation of K-12 enrollment to HS grad rate: –0.1734).
The most confident statement one can make from these data is that within South Dakota, relatively higher teacher salaries are a very weak predictor of student performance on the ACT.
Tangentially related: The Department of Education lists 66 out of 151 districts as having opted out of the general fund levy. Interestingly, opt-outs don't mean higher teacher salaries: the correlation on those two columns is actually negative, –0.1975.