Assessment of arts educators, including music educators, has evolved into a high-stakes situation that drives teacher pay, promotion, and retention. This assessment process is driven by federal policy advocating for a value-added model based on student performance. Principals, who are often charged with assessing artistic musical performance, traditionally conduct these evaluations but may be underprepared to do so. This disconnect between evaluator expertise and teacher assessment expectations poses a challenge for arts educators, administrators, and policymakers. This article presents a policy model for music teacher assessment based on findings from a study of principals’ expectations of entry-year instrumental music teachers (EYTs) and how these expectations are communicated. I first outline this study and then explain how these findings are relevant for music teacher assessment, especially within a value-added model. Principal expectations are especially important to articulate, given the high-stakes nature of teacher assessment and the direct connection between expectations and assessment. After speaking with both principals and EYTs, I derived the following conclusions: (a) principals’ expectations largely focus on interpersonal and general teaching skills such as engaging students and classroom management, not on musical expertise; (b) principals’ expectations are often not adequately conveyed to EYTs, and assessments are conducted primarily through official reviews; and (c) increased communication of principal expectations would benefit the EYT's induction process. I suggest that principals and music teachers increase communication and dialogue to define “musical success” and determine adequate methods for music teacher assessment. Finally, I conclude by presenting a new model linking policy with music teacher assessment.