Daniel Koretz is the Henry Lee Shattuck Professor of Education at the Harvard Graduate School of Education. His research focuses on educational assessment and policy, particularly the effects of high-stakes testing on educational practice and the validity of score gains. He is the author of "Measuring Up: What Educational Testing Really Tells Us" (Harvard University Press, 2008). Koretz comments here that he finds it distressing after generations of work and countless articles and chapters, that those in the field still cannot agree on what validity means. As someone who has worked for three decades to persuade people of the need to devote more focus to the evaluation of impact, Koretz argues he would find it helpful if more colleagues would use simple language that people outside of the field understand when making the argument for "impact" in order to make the term "validity" useful.