The Allure Of Teacher Quality
Those following education know that policy focused on "teacher quality" is by far the dominant paradigm for improving schools over the past few years. Some (but not nearly all) components of this all-hands-on-deck effort are perplexing to many teachers, and have generated quite a bit of pushback. No matter one’s opinion of this approach, however, what drives it is the tantalizing allure of variation in teacher quality.
Fueled by the ever-increasing availability of detailed test score datasets linking teachers to students, the research literature on teachers’ test-based effectiveness has grown rapidly, in both size and sophistication. Analysis after analysis finds that, all else being equal, the variation in teachers’ estimated effects on students' test growth – the difference between the “top” and “bottom” teachers – is very large. In any given year, some teachers’ students make huge progress, others’ very little. Even if part of this estimated variation is attributable to confounding factors, the discrepancies are still larger than most any other measured "input" within the jurisdiction of education policy. The underlying assumption here is that “true” teacher quality varies to a degree that is at least somewhat comparable in magnitude to the spread of the test-based estimates.
Perhaps that's the case, but it does not, by itself, help much. The key question is whether and how we can measure teacher performance at the individual level and, more importantly, influence the distribution – that is, to raise the ceiling, the middle and/or the floor. The variation hangs out there like a drug to which we’re addicted, but haven’t really figured out how to administer. If there was some way to harness it efficiently, the potential benefits could be considerable. The focus of current education policy is in large part an effort to do anything and everything to try and figure this out. And, as might be expected given the enormity of the task, progress has been slow.