That includes the normal structural moves in schools, like moving from sixth grade to seventh grade and changing from elementary school to junior high. When you do that, you lose ground. We find that schools with more turnover in them hurt the students that don't move. So if you're in a high turnover school, that hurts you, even though you don't move. Now, some moves are voluntary and some are somewhat involuntary.
Some people have to move for economic reasons, financial circumstances, job loss, or whatever.
Those moves look like moves to get to better schools. What really hurts is if you move within the same district. If you're churning around in the same district, then you're in trouble. Clowes The President has said that our tax dollars shouldn't go to support what doesn't work. I don't think there's much evidence.