Researchers consider the transformative changes in teacher evaluation systems following the Race to the Top initiative, emphasizing the adoption of multiple performance measures such as value-added measures and classroom observations. While the majority of states and districts underwent revisions, California notably abstained from statewide reforms. Despite the spotlight on using student test scores, most teachers' ratings primarily stem from classroom observations, especially those teaching non-tested subjects. Initially lacking evidence, recent studies, notably the Excellence in Teaching Project in Chicago Public Schools, reveal that in-depth teacher evaluations focusing on classroom interactions can enhance teaching practices and, consequently, student outcomes. However, these advancements require substantial time commitments from observers, typically principals, and teachers, coupled with comprehensive training and ongoing support. Crucially, while these evaluations demonstrated positive impacts overall, schools facing lower performance and higher poverty witnessed less progress, underscoring the necessity for added resources and support. As California deliberates its evaluation system revisions, researchers urge policymakers to prioritize resources and support for comprehensive teacher evaluations, recognizing their pivotal role in fostering student achievement.