Colorado’s Questionable Use Of The Colorado Growth Model
I have been writing critically about states’ school rating systems (e.g., Ohio, Florida, Louisiana), and I thought I would find one that is, at least in my (admittedly value-laden) opinion, more defensibly designed. It didn’t quite turn out as I had hoped.
One big starting point in my assessment is how heavily the systems weight absolute performance (how highly students score) versus growth (how quickly students improve). As I’ve argued many times, the former (absolute level) is a poor measure of school performance in a high-stakes accountability system. It does not address the fact that some schools, particularly those in more affluent areas, serve students who, on average, enter the system at a higher-performing level. This amounts to holding schools accountable for outcomes they largely cannot control (see Doug Harris’ excellent book for more on this in the teacher context). Thus, to whatever degree testing results can be used to judge actual school effectiveness, growth measures, while themselves highly imperfect, are to be preferred in a high-stakes context.
There are a few states that assign more weight to growth than absolute performance (see this prior post on New York City’s system). One of them is Colorado’s system, which uses the well-known “Colorado Growth Model” (CGM).*
In my view, putting aside the inferential issues with the CGM (see the first footnote), the focus on growth in Colorado’s system is in theory a good idea. But, looking at the data and documentation reveals a somewhat unsettling fact: There is a double standard of sorts, by which two schools with the same growth score can receive different ratings, and it’s mostly their absolute performance levels determining whether this is the case.
