It's easier to pick a good teacher than to train one: Familiar and new results on the correlates of teacher effectiveness.

Neither holding a college major in education nor acquiring a master’s degree is correlated with elementary and middle school teaching effectiveness, regardless of the university at which the degree was earned. Teachers generally do become more effective with a few years of teaching experience, but we also find evidence that teachers may become less effective with experience, particularly later in their careers. These and other findings with respect to the correlates of teacher effectiveness are obtained from estimations using value-added models that control for student characteristics as well as school and (where appropriate teacher) fixed effects in order to measure teacher effectiveness in reading and math for Florida students in fourth through eighth grades for eight school years, 2001–2002 through 2008–2009.