Discussions of teacher turnover usually focus on "how many" teachers leave schools each year, without regard for their performance in the classroom. This oversimplification masks the real teacher retention crisis: not only a failure to retain enough teachers, but a failure to retain the "right" teachers. This executive summary presents findings of…

"Irreplaceables" are teachers who are so successful they are nearly impossible to replace, but who too often vanish from schools as the result of neglect and inattention. To identify and better understand the experience of these teachers, the authors started by studying 90,000 teachers across four large, geographically diverse urban school…