We study a teacher incentive policy in Washington State that awards a financial bonus to National Board certified teachers in high poverty schools. Using a regression discontinuity design, we find that the bonus policy increased the proportion of certified teachers in bonus-eligible schools by improving hiring, increasing certification rates of incumbent teachers, and reducing turnover. Depending on the method, we estimate that the proportion of NBCTs in treated schools increased by about four to eight percentage points over the first five years of eligibility. However, the improvement in certification rates corresponds to a change of about 0.2-0.3% of a standard deviation in teacher quality per year and we do not find evidence that the bonus resulted in detectible effects on student test achievement.