I don't believe that even the best teachers can completely overcome the huge deficits in socialization, motivation and intellectual development that poor students bring to class through no fault of their own. They can help narrow the gap between these students and those from advantaged backgrounds, but they can't eliminate it. That's a vital distinction given short shrift in today's debate. It's one thing to improve academic performance in absolute terms, but it's quite another to improve performance in relative terms.
And not just concerning teacher quality -- education reform in general.