In November 2006, the U.S. Department of Education issued new rules making it easier for schools and districts to use gender-separate classes, programs and activities as a strategy for enhancing educational achievement and opportunity. Education Secretary Margaret Spellings described the revised Title IX regulations as part of a greater effort to expand and diversify options in the public sector. "Every child should receive a high-quality education in America, and every school district deserves the tools to provide it," she said. The federal action is expected to accelerate efforts by public school systems to experiment with single-sex education, particularly in inner-city and charter schools. In announcing the new regulations, Secretary Spellings pointed to a federally sponsored review of research on same-sex schooling that suggests educating boys and girls separately--either in different schools or separate classes--"may provide benefits to students under certain circumstances." This issue of "The Progress of Education Reform" features highlights of that research review and of a similarly comprehensive analysis published recently by the United Kingdom's Centre for Education and Employment Research. Taken together, they provide a useful, up-to-date look at what individuals knows--and what they don't--about the relative merits of same-sex versus coeducational schooling. This issue also offers links to other sources of information on the topic and additional details about the revised Title IX regulations.