This study considers the efficacy of a certification system for teachers established by the National Board for Professional Teaching Standards (NBPTS). The authors utilize a four-year span of the longitudinal data from Florida to determine the relationship between teacher NBPTS certification and student test scores on low-stakes and high-stakes exams. They find evidence that NBPTS certification provides a positive signal of teacher productivity in some cases, but it is highly variable. The process of becoming NBPTS certified does not appear to increase teacher productivity nor do NBPTS-certified teachers appear to enhance the productivity of their colleagues.