Birds of a feather, flock together. That's the finding from a new study exploring patterns in teacher transfers. In other words, high performing teachers tend to transfer to schools with a large proportion of other high performing teachers (and also high performing students), while low performing teachers tend to cluster in bottom quartile schools.

The trends found in this CALDER study result in what the authors Li Feng and Tim Sass describe as the "rich getting richer" phenomenon, feeding and exacerbating differences in teacher quality between schools. One way the authors propose easing the natural flow of high performing teachers to already high performing schools is to offer salary differentials for highly effective teachers willing to re-locate to schools serving more disadvantaged students, effectively also shutting down the pattern of weak teachers filling those spots. This solution is something that a handful of Florida districts now have in their contracts. It's been recently expanded, thanks to new state law offering salary supplements for teachers both in Title I schools and schools in the bottom two categories of school improvement.