In March, 2004, the federal Department of Education issued proposed Title IX regulations that promise to provide public school districts and charter school organizers considerable flexibility in establishing single-sex classes and schools. At the same time, however, as part of the No Child Left Behind Act, the Department has called for "scientifically based" research to guide educational practices while the Supreme Court has ruled that state actors need an "exceedingly persuasive" justification for drawing distinctions on the basis of sex. The dramatic turnaround in federal policy and the seeming inconsistencies in the law have sparked heated debate that has plumbed the depths of gender, race, and ideology. Yet both sides concur that research findings supporting single-sex schooling are inconclusive. This article works through this conundrum, maintaining that social science evidence has far more to offer the debate than either supporters or detractors of single-sex schooling recognize. To validate that assertion, it examines data on academic performance and social deficits across gender and race as well as tentative evidence from existing programs. Based on these findings, the author draws the critical connection among program planning, implementation, and assessment and urges educators and researchers to explore a broad range of questions and methods both in their search for evidence to inform and guide program development and in their efforts to generate new findings that will prove instructive if not definitive in measuring the overall effects of these programs.