John Thompson (making an important point while uncharacteristically losing control of his syntax, but hey, it's a blog):
It is unusual for high-performing teachers to leave their high-performing schools for low-performing or high-poverty schools. And many of them move to high-poverty, high-performing selective schools. But, Calder crunched this data for 13,456 secondary Reading teachers in two states. Only, 109 shifted to a higher-poverty school!