Talk about test scores is often imprecise, writes Matthew DiCarlo on Shanker Blog. For example, “schools with high average test scores are not necessarily ‘high-performing,’ while schools with lower scores are not necessarily ‘low-performing’,” he writes.
As we all know, tests don’t measure the performance of schools. They measure (however imperfectly) the performance of students.
Instead, to the degree that school (and teacher) effectiveness can be assessed using testing data, doing so requires growth measures, as these gauge (albeit imprecisely) whether students are making progress, independent of where they started out and other confounding factors.