Data-based decision making is all the rage. Secretary of Education Arne Duncan (2009) has emphatically declared, "I am a deep believer in the power of data to drive our decisions. Data gives us the roadmap to reform. It tells us where we are, where we need to go, and who is most at risk." In the past few years, all 50 states have adopted most or all of the Data Quality Campaign's framework for state data systems. In important respects, this is a welcome development. Data expose inequities, create transparency, and help drive organizational improvement. But something is amiss. Many educators regard talk of data-based decision making as an external imposition, sensing new obligations and what they see as a push to narrow schooling to test scores and graduation rates. Data can be a powerful tool. But one must recognize that collecting data is not "using" data; that data are an input into judgment rather than a replacement for it; that data can inform but not resolve difficult questions of politics and values; and that the country needs better ways to measure what matters, rather than valuing those things it can measure.