Are there important determinants of teacher productivity that are not captured by teacher credentials but that can be measured by subjective assessments? And would evaluating teachers based on a combination of subjective assessments and student outcomes more accurately gauge teacher performance than student test scores alone? Using data from a midsize Florida school district, this paper explores both questions by calculating teachers' "value added" and comparing those outcomes with subjective ratings of teachers by school principals. Teacher value-added and principals' subjective ratings are positively correlated and principals' evaluations are better predictors of a teacher's value added than traditional approaches to teacher compensation focused on experience and formal education. Also, teachers' subject knowledge, teaching skill, and intelligence are most closely associated with both the overall subjective teacher ratings and the teacher value added.