The authors, who have worked with more than 2,000 schools across the United States in efforts to close gender gaps, describe how gender-related issues consistently intersect and interfere with school improvement efforts. They present statistics showing that schools are now failing boys in more areas than girls, and describe how "the structures, expectations, and teaching styles found in traditional classrooms" generally favor girls over boys. They point out that students are individuals and there is a great deal of overlap in the learning characteristics of the two genders, and they assert that instructional strategies that are effective for teaching boys--incorporating more movement, visual-spatial projects, and choice--can benefit both boys and girls as well as close gender gaps. This article addresses the topics of achievement gaps and single-sex education.