Under the "Every Student Succeeds Act," states and local school districts have more flexibility to design and implement teacher evaluation systems; however, very few studies have empirically examined the issue of localization of teacher evaluation policies. This study draws on longitudinal, mixed-methods evidence from school districts in a state to examine the implementation and potential effects of teacher evaluation policy on student achievement. We found that the state's new teacher evaluation policy appeared to have null effects on student reading and mathematics achievement. Our interview data suggested that challenges in implementing the policy at each district can explain such findings.