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Education agencies are evaluating teachers using student achievement data. However, very little is known about the comparability of test-based or "value-added" metrics across districts and the extent to which they capture variability in classroom practices. Drawing on data from four urban districts, we find that teachers are categorized differently when compared within versus across districts. In addition, analyses of scores from two observation instruments, as well qualitative viewing of lesson videos identify stark differences in instructional practices across districts among teachers who receive similar within-district value-added rankings. Exploratory analyses suggest that these patterns are not explained by observable background characteristics of teachers and that factors beyond labor market sorting likely play a key role.
Presented at the American Education Research Association (AERA) Annual Meeting, Philadelphia, PA.