A study of 100 principals from Miami-Dade County Public Schools finds that while teacher effectiveness varies substantially, principals’ evaluations of teachers often fail to differentiate performance among teachers. In this study, researchers Jason A. Grissom and Susanna Loeb offer new evidence on principals’ subjective evaluations of their teachers’ effectiveness using two sources of data from a large, urban district: principals’ high-stakes personnel evaluations of teachers, and their low-stakes assessments of a subsample of those teachers provided to the researchers. The researchers find that principals’ evaluations of teachers are quite positive whether the stakes are high or low, but the low-stakes evaluations show substantially more use of lower rating categories, and many teachers rated ineffective on the low-stakes assessment receive “effective” or “highly effective” high-stakes ratings. Teacher characteristics, such as experience, partially explain the discrepancy between the two scores. Also, despite the fact that principals overwhelmingly assign teachers to the two highest rating categories on the high-stakes evaluation, their high- and low-stakes ratings show similar correlations with teacher value-added measures.
For this study, see http://www.mitpressjournals.org/doi/abs/10.1162/EDFP_a_00210
Another study has similar findings. Matthew A. Kraft of Brown University and Allison F. Gilmour of Vanderbilt University revisit TNTP’s 2009 findings that districts fail to recognize and act on differences in teacher effectiveness. The researchers compiled teacher performance ratings across 24 states that adopted major reforms to their teacher evaluation systems. In the vast majority of these states, the percentage of teachers rated Unsatisfactory remains less than 1%. However, the full distributions of ratings vary widely across states with 0.7% to 28.7% rated below Proficient and 6% to 62% rated above Proficient. The authors present original survey data from an urban district illustrating that evaluators perceive more than three times as many teachers in their schools to be below Proficient than they rate as such. Interviews with principals reveal several potential explanations for these patterns.