Over the past three years, more than 20 US states have passed legislation establishing new teacher evaluation requirements and systems, and even more have committed to do so in Race to the Top or Elementary and Secondary Education Act Flexibility Waiver applications. These new evaluation systems have real potential to foster a more performance-oriented public education culture that gives teachers meaningful feedback about the quality and impact of their work. But there are pitfalls in states' rush to legislate new systems, and there are real tensions and trade-offs in their design. Unfortunately, much of the current policy debate has been framed in stark ideological terms that leave little room for adult discussion of these tensions. This paper seeks to move the debate beyond ideology and technical issues by highlighting four key tensions that policymakers, advocates, and educators must consider in the development of new teacher evaluations: (1) Flexibility versus control; (2) Evaluation in an evolving system; (3) Purposes of evaluations; and (4) Evaluating teachers as professionals. Recognizing these tensions and trade-offs, this paper offers several policy recommendations: (1) Be clear about the problems new evaluation systems are intended to solve; (2) Do not mistake processes and systems as substitutes for cultural change; (3) Look at the entire education ecosystem; (4) Focus on improvement, not just deselection; (5) Encourage and respect innovation; (6) Think carefully about waivers versus umbrellas; (7) Do not expect legislation to do regulation's job; and (8) Create innovation zones for pilots--and fund them. (Contains 24 notes.)