Is a good elementary teacher always good? Assessing teacher performance estimates across subjects

In most elementary schools, teachers are responsible for several subjects. Various personnel policies, such as evaluating teachers based on value-added estimates aggregated across subjects or departmentalizing teachers, implicitly make assumptions about how closely teacher effectiveness is aligned across subjects. This paper reports on research exploring these issues using student-teacher linked data from North Carolina to assess the correlation of teacher productivity across math and reading. We find correlations of value-added estimates of about 0.6 and correlations in the underlying teacher effectiveness of 0.7-0.8. Assigning teachers to teach particular subjects based on their measured productivity could yield modest student achievement benefits.