I've heard a lot of people question the wisdom of teacher transfers based on the reasoning that a teacher who's effective in one school setting might not be as effective in another, due to differences in the student population, the culture of the school, or the pedagogy/curricula.
So far there's been precious little research literature on this topic, but a new working paper from the National Bureau of Economic Research indicates that there are good reasons to investigate it in depth.
Analyzing a set of matched student-teacher data in North Carolina between 1995 and 2006, researcher C. Kirabo Jackson found that what he calls "match quality"—the factors that make a teacher more productive in one school setting than another—can account for up to a quarter of the observable "teacher effect," i.e., how effective a teacher appears to be at raising his or her students' academic achievement.
He also found that the teachers studied tended to be more effective in mathematics after they moved to a new school. That finding suggests that they are actively seeking out schools with a better match for their talent. Teachers were also less likely to leave their current school when the "match quality" was high.
"Part of what we typically interpret as a teacher quality effect is in fact a match quality effect that may not be portable across schooling environments," Jackson writes in the paper.
This is potentially an important thing to consider, especially in the context of the "equitable distribution" of teachers. Typically, that phrase refers to policies and incentives to encourage teachers who are the most effective to transfer to—and stay in—schools with high percentages of disadvantaged or minority students, or to keep highly effective teachers from transferring away from such schools.
After all, if a large part of teacher effectiveness is related to match quality, and if teachers themselves are responding to match quality in their choice of workplace, then equitable-distribution policies probably need to take into account which teacher-school pairings are the most successful.