This paper describes the results of a study of the relationship between teacher certification by the National Board for Professional Teaching Standards (NBPTS) and elementary-level student achievement. Researchers examined whether NBPTS assesses the most effective applicants, whether its certification indicates teacher quality, and whether completing the NBPTS assessment process helps increase teacher effectiveness. Although the findings indicate that NBPTS identifies the more effective applicants and that National Board Certified Teachers are generally more effective than teachers who never applied to the program, the magnitude of the "NBPTS effect" differs significantly by grade level and student type. There is no evidence that the NBPTS certification process itself increases teacher effectiveness.