We use value-added models to calculate measures of effectiveness for new elementary school teachers in Florida between 2001-02 and 2005-06, then compare the attrition and mobility patterns of more and less effective teachers overall and across various types of schools. While we do not find evidence that schools are disproportionately losing their most effective early career teachers, our data nonetheless suggest that there is considerable room for schools to raise student achievement and close achievement gaps through targeted policies aimed at retaining only their most effective performers. A clear majority of the state’s most effective teachers do not remain in their initial schools only four years into their career, and these same teachers are no less likely to leave the profession altogether than are the least effective. Schools with high performing students do a far better job than most of retaining their most effective teachers and dismissing the least effective.

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