For many years, the conventional wisdom was that teachers' experience had little bearing on their effectiveness after a few years on the job. This perception has sometimes been used to justify underinvestment in policies aimed at retaining teachers. Yet most rigorous studies over the past two decades have found that, on average, teachers continue to improve as they accumulate additional experience, especially in environments that support professional learning and collaboration. This brief addresses the value of teaching experience based on recent research, summarizes the conditions that foster ongoing teacher improvement, and explores potential implications of this work for federal, state, and local policy. The common refrain that teaching experience doesn't matter after the first few years in the classroom is not supported by the evidence. Rather, it has become increasingly clear that teachers continue to improve well into the second decade of teaching, albeit more gradually than they do initially. Four recommendations are provided to policymakers to support teachers' continued growth and retainment.