In "The Irreplaceables," TNTP researchers argued that America's urban schools take a negligent approach to teacher retention, losing too many of their very best teachers--their "Irreplaceables"--and keeping too many of their weakest teachers, year after year. A combination of weak school leadership, poor working conditions and restrictive policies…

"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…