In this study, we consider the efficacy of a relatively new and widely accepted certification system for teachers established by the National Board for Professional Teaching Standards (NBPTS). We utilize an extensive database covering the universe of teachers and students in Florida for a four-year span to determine the relationship between NBPTS certification and the impact of teachers on student test scores from both low-stakes and high-stakes exams. Contrary to some previous studies, we find evidence that NBPTS certification provides a positive signal of a teacher's contribution to student achievement only in a few isolated cases. However, our results do reinforce evidence from previous research that the process of becoming NBPTS certified does not increase teacher productivity. (Contains 36 footnotes and 8 tables.)