Teacher Effects and Teacher Effectiveness: A Validity Investigation of the Tennessee Value Added Assessment System

Abstract

This article addresses the validity of teacher evaluation measures produced by the Tennessee Value Added Assessment System (TVAAS). The system analyzes student test score data and estimates the effects of individual teachers on score gains. These effects are used to construct teacher value-added measures of teaching effectiveness. We describe the process of generating teacher effectiveness estimates in TVAAS and discuss policy implications of using these estimates for accountability purposes. Specifically, the article examines the TVAAS definition of teacher effectiveness, the mechanism employed in calculating numerical estimates of teacher effectiveness, and the relationships between these estimates and student ability and socioeconomic background characteristics. Our validity analyses point to several logical and empirical weaknesses of the system, and underscore the need for a strong validation research program on TVAAS.