In recent years, states have sought to increase accountability for public school teachers by implementing a package of reforms centered on high-stakes evaluation systems. We examine the effect of these reforms on the supply and quality of new teachers. Leveraging variation across states and time, we find that accountability reforms reduced the number of newly licensed teacher candidates and increased the likelihood of unfilled teaching positions, particularly in hard-to-staff schools. Evidence also suggests that reforms increased the quality of new labor supply by reducing the likelihood new teachers attended unselective undergraduate institutions. Decreases in job security, satisfaction, and autonomy are likely mechanisms for these effects.