This paper reviews prior research to assess the effectiveness of Title I in closing the achievement gaps of disadvantaged students vis-à-vis their non-disadvantaged counterparts. A research synthesis approach is adopted to summarize national assessments of Title I conducted between 1966 and 2011. These analyses are supplemented by the authors' analysis of NAEP data from 1990 to 2013. There is no evidence that early Title I programs significantly reduced achievement gaps nationwide. Studies following NCLB implementation show modest closure of grade 4 gaps of about 0.2 of a standard deviation. Given the modest academic gains attributable to Title I, and considering that the program costs about $15 billion per year, the authors conclude that Title I programs have not been cost effective in closing the achievement gaps.