Since US state policy makers reformed their teacher evaluation systems in the mid-2010s, the scholarly literature has paid little attention to the classroom-level measures of student learning growth that many states repurposed as teacher performance measures. This study addresses the gap by documenting teachers' and principals' experiences with the measures commonly known as student learning objectives (SLOs). After conducting a qualitative examination of survey and interview data from principals and teachers in 17 states, the author echoes critics' concerns that SLOs are a flawed means for determining teachers' effectiveness. Although proponents presented SLOs as a flexible and empowering evaluation alternative, districts' attempts to standardize the often-manipulated performance measures alienated teachers. Many principals believed SLOs took time away from more valued efforts to improve their schools. The article concludes with a discussion about managing the difficult balance between holding teachers accountable and supporting their growth.