Jersey Jazzman: NJ's Student Growth Measures (SGPs): Still Biased, Still Used Inappropriately

Jersey Jazzman: NJ's Student Growth Measures (SGPs): Still Biased, Still Used Inappropriately

NJ's Student Growth Measures (SGPs): Still Biased, Still Used Inappropriately

What follows is yet another year's worth of data analysis on New Jersey's student "growth" measure: Student Growth Percentiles (SGPs).

And yet another year of my growing frustration and annoyance with the policymakers and pundits who insist on using these measures inappropriately, despite all the evidence.

Because it's not like we haven't looked at this evidence before. Bruce Baker started back in 2013, when SGPs were first being used in making high-stakes decisions about schools and in teacher evaluations; he followed up with a more formal report later that year.

Gerald Goldin, a professor emeritus at Rutgers, expressed his concerns back in 2016. I wrote about the problems with SGPs in 2018, including an open letter to members of the NJ Legislature.

But here we are in 2019, and SGPs continue to be employed in assessments of school quality and in teacher evaluations. Yes, the weight of SGPs in a teacher's overall evaluation has been cut back significantly, down to 5 percent -- but it's still part of the overall score. And SGPs are still a big part of the NJDOE's School Performance Reports.

So SGPs still matter, even though they have a clear and substantial flaw -- one acknowledged by their creator himself --  that renders them invalid for use in evaluating schools and teachers. As I wrote last year:

It's a well-known statistical precept that variables measured with error tend to bias positive estimates in a regression model downward, thanks to something called attenuation bias. Plain English translation: Because test scores are CONTINUE READING: Jersey Jazzman: NJ's Student Growth Measures (SGPs): Still Biased, Still Used Inappropriately