Most analyses of teacher quality end without any assessment of the economic value of altered teacher quality. This paper combines information about teacher effectiveness with the economic impact of higher achievement. It begins with an overview of what is known about the relationship between teacher quality and student achievement. This provides the basis for consideration of the derived demand for teachers that comes from their impact on economic outcomes. Alternative valuation methods are based on the impact of increased achievement on individual earnings and on the impact of low teacher effectiveness on economic growth through aggregate achievement. A teacher one standard deviation above the mean effectiveness annually generates marginal gains of over $400,000 in present value of student future earnings with a class size of 20 and proportionately higher with larger class sizes. Alternatively, replacing the bottom 5-8 percent of teachers with average teachers could move the U.S. near the top of international math and science rankings with a present value of $100 trillion. It has become widely accepted that high quality teachers are the most important asset of schools, but this recognition has not led to any consensus on the appropriate policies that should be followed to ensure that we have a good stock of teachers. The policy proposals range quite broadly, although generally they call either for closer regulation of quality or for more use financial incentives with little in between these two poles. Remarkably, these policy deliberations seldom include even the most rudimentary economic analyses or evaluations. The focus of most educational policy research and of the majority of public discussions of school policy is simply whether or not some school input has a significant positive impact on student achievement and not what it might cost or the economic benefits it might produce.1 This paper focuses on the demand side of the teacher labor market in the United States and provides baseline estimates of the economic value of improving teacher quality.Much of the discussion about the potential demand for teachers is framed in terms of ensuring sufficient numbers of trained teachers. This, however, is not really the issue, because the U.S. has have for a long time trained considerably more teachers than the number of positions that annually become open in schools. For example, in 2000 86,000 recent graduates entered into teaching, even though 107,000 graduated with an education degree the year before (see Provasnik and Dorfman (2005), U.S. (2009)). 2 At the same time, many have noted shortages of teachers in particular 1 One notable exception is the long term emphasis by Henry Levin and his co-authors on comparing benefits and costs, although this has not developed much traction in policy debates. See, for example, Levin and McEwan (2001) and Belfield and Levin (2007). An early attempt at benefit-cost analysis in the case of class size reduction is found in Krueger (2002), following a conceptually similar...