What value do standardized observation systems add to summative teacher evaluation systems?

Teacher evaluation systems work to balance summative and formative goals. Instructional observations are an important part of such systems, allowing evaluation to directly impact instruction. Research shows that summative and formative goals can conflict with each other. This paper examines whether the summative usage of observation scores contributes to summative evaluation. We find that, after accounting for traditional principal ratings, observation scores provide little predictive validity for identifying high quality teachers. Given the reviewed negative impacts of summative uses of observation scores in teacher evaluation, teacher evaluation systems should reconsider the summative usage of observation scores. • Observation Systems are used within teacher evaluation systems to address both summative and formative goals. • The summative usage of observation systems has negative consequences for their formative usage. • Our analyses suggest little positive benefit of using observation systems summatively. • Holistic principal ratings are equally predictive of teacher quality as scores from observation systems. • The summative usage of observation systems should be strongly reconsidered.