The proposition that expanding pre-K will improve later achievement for children from low-income families is premature. Premature as well is the presumption that solid research exists to guide the content and structure of pre-K programs. Despite more than 50 years of preliminary work on pre-K as an early intervention for young children from poor backgrounds, the field of early childhood education has a relatively small database to use as a guide to effective practice. In this paper, the author argues that lack of evidence about which skills and dispositions are most important to effect in pre-K and what instructional practices would affect them has led us to the current situation of poorly defined, enormously varied programs, all called pre-K, as well as a reliance on a set of quality measures with no empirical validity. Despite being included in national and state policies and used to hold pre-K providers accountable, none of the widely used measures of classroom and center quality relates strongly, if at all, to child growth on the school readiness outcomes on which most pre-K programs are focused. The outlook for poor children is too dire to allow this situation to continue. Contains endnotes.