The national educational challenge was most forcefully articulated by the nation’s governors in 1989. As they met in Charlottesville, Virginia, they felt the need of the nation to improve the performance of students—a need articulated a half decade previously in A Nation at Risk (National Commission on Excellence in Education 1983). And they declared that the United States should be first in the world in mathematics and science by the turn of the century (National Education Goals Panel 1991). The problem was that we had no experience to draw upon that would indicate how this could be done. In the intervening two decades we have come to recognize that improving teacher effectiveness is perhaps the only viable way to accomplish the governors’ goals, but even there the policies and mechanisms are far from obvious. This discussion provides a quantitative statement of one approach to achieving the governors’ (and the nation’s) goals—teacher deselection. Specifically, how much progress in student achievement could be accomplished by instituting a program of removing, or deselecting, the least-effective teachers? A variety of policies for hiring and retraining teachers have been proposed, but they have not been very successful in the aggregate, as student performance has not improved. At the same time, it is widely recognized that some teachers do a very poor job, and few people believe that the worst teachers can be transformed into good teachers. What would happen if we simply adopted policies of systematically removing the most ineffective teachers?