This graph, published in Science earlier this month, illustrates two things: 1) the cost of "churn" in the teaching profession is significant; and 2) its effects differ across subject areas.

The graph, which accompanied an article titled "The Effects of Experience and Attrition for Novice HIgh-School Science and Mathematics Teachers," by Gary T. Henry, C. Kevin Forner and Kevin C. Bastian, shows how the test scores of students improved as their teachers became more experienced, during the teachers' first five years in classrooms....