A Case for Evaluating Teachers

Education researchers and policymakers have increasingly turned their attention to improving teacher effectiveness. The issue is particularly important because teacher quality matters greatly but varies widely. The difference between an average math teacher and an excellent one is estimated to translate into an increase of $20,000 in a student’s lifetime earnings.

In a 2011 working paper, “The Effect of Evaluation on Performance: Evidence from Longitudinal Student Achievement Data of Mid-career Teachers,” Eric Taylor and John Tyler investigate the effectiveness of Cincinnati Public School’s Teacher Evaluation System (TES), an intensive program that includes four classroom observations per year and detailed feedback from former top educators trained as evaluators. Evaluations measure preparedness, classroom management, and overall teacher performance during the observation. Three of the four observations are unannounced, motivating teachers to be prepared in the classroom. Receipt of a poor TES evaluation can lead to contract non-renewal, while an exceptional review can result in promotion to “Lead Teacher” status and a $6,000 salary increase.

Taylor and Tyler examine the effectiveness of mid-career teachers, measured by student math scores, before and after participating in TES. They find that participation is associated with a student math score increase of 0.113 standard deviations. Math scores increase an average of 0.066 standard deviations during the year of teacher evaluations.

An increase in standardized math scores of 0.113 standard deviations translates into an additional $200,000 in expected student lifetime earnings for a class of 20 students. Considering that the positive effects on teacher training persist several years after the program, the total benefits of TES are a multiple of $200,000. While the cost of evaluating one teacher through TES is about $20,000 per year, each teacher participates in TES once every five years, which reduces the annual cost of TES to around $4,000 per teacher. Thus, the benefits of TES significantly outweigh the costs.

Further research is needed to isolate the most valuable elements of teacher evaluations in order to decrease cost and increase efficacy. Most schools currently implement teacher evaluations on a yearly basis. Results of TES, however, suggest that evaluation only once every five years may increase cost effectiveness. Importantly, TES has a limited impact on reading scores, suggesting that different subjects may require different evaluation systems.