Background/Context: The stakes are getting higher for teachers daily as more and more states adopt hiring, firing, and tenure-granting policies based on teacher evaluations. Even more concerning is the limited discussion about whether or not high-stakes teacher evaluation can meet the intended outcome of improved student achievement, and at what cost. These high-stakes decisions are based on the rationale that firing ineffective teachers (as primarily measured by observation data and value-added scores) will improve student achievement. This premise is challenged by various variables and assumptions (e.g., reliability, validity, percentage fired, and turnover) that, if not met, could result in a number of possible unintended consequences. Focus of Study: This paper examines the history of high-stakes teacher evaluation and the ways in which teacher evaluation data are being used in today's schools to make human capital decisions. The intended consequences and unintended consequences are explored in great detail. Research Design: This paper is an analytic essay. Conclusions/Recommendations: There is no evidence that high-stakes teacher evaluation can produce a more effective teacher workforce and improve student achievement. Even if basic requirements and assumptions are met (e.g., highly reliable and valid measures, retention of effective teachers, and highly effective hires), gains in student achievement may be short lived, insignificant, or practically meaningless. The possible unintended consequences could result in worse, rather than better, student achievement outcomes and increase the gap in opportunity to learn for students attending the most and least affluent schools.