Critics of test-based accountability warn that test preparation has a negative influence on teachers' instruction due to a focus on procedural skills. Others advocate that the adoption of more rigorous assessments may be a way to incentivize more ambitious test preparation instruction. Drawing on classroom observations and teacher surveys, we do find that test preparation activities predict lower quality and less ambitious mathematics instruction in upper-elementary classrooms. However, the magnitudes of these relationships appear smaller than the prevailing narrative has warned. Further, our findings call into question the hypothesis that test rigor can serve as a lever to elevate test preparation to ambitious teaching. Therefore, improving the quality of mathematics instruction in the midst of high-stakes testing likely will require that policymakers and school leaders undertake comprehensive efforts that look beyond the tests themselves.