Over the past decade, many states enacted substantial reforms to teacher-related laws and policies. In Michigan, the state legislature implemented requirements for teacher evaluation based partly on student achievement, reduced tenure protections, and restricted the scope of teacher collective bargaining. Some teacher advocates view such reform as a “war on teachers,” but proponents argue these policies may have enabled personnel decisions that positively impact student performance. Evidence on this debate remains limited. In this study, we use detailed administrative data from all Michigan traditional public schools from 2005–06 to 2014–15. We estimate event study models exploiting the plausibly exogenous timing of collective bargaining agreement expirations. Across a variety of samples and specification checks, we find these reforms had generally null results, with some evidence of heterogeneity by cohort. We investigate several possible mechanisms and conclude that districts with more restrictive teacher contracts prior to reform and districts with more rigorous use of teacher evaluations experienced more positive impacts after reform exposure.