This story originally appeared in The Washington Post.
Academic scholars are often dismayed when policymakers pass laws that disregard or misinterpret their research findings. The use of value-added methods (VAMS) in education policy is a case in point.
About a decade ago, some researchers reported that teachers are the most important school-level factor in students’ learning, and that that their effectiveness varies widely within schools (McCaffrey, Koretz, Lockwood, & Hamilton 2004; Rivkin, Hanushek, & Kain 2005; Rockoff 2004). Many policymakers interpreted these findings to mean that teacher quality rests with the individual rather than the school and that, because some teachers are more effective than others, schools should concentrate on increasing their number of effective teachers.
Based on these assumptions, proponents of VAMS began to argue that schools could be improved substantially if they would only dismiss teachers with low VAMS ratings and replace them with teachers who have average or higher ratings (Hanushek 2009). Although panels of scholars warned against using VAMS to make high-stakes decisions because of their statistical limitations (American Statistical Association, 2014; National Research Council & National Academy of Education, 2010), policymakers in many states and districts moved quickly to do just that, requiring that VAMS scores be used as a substantial component in teacher evaluation...