Countries around the world have achieved huge gains in primary education, reaching a world average of 83.8 percent in net primary enrollment. However, large numbers of students still do not complete primary education, and even fewer continue on to secondary school. Since so few children complete primary school, those who do must be able to continue their schooling. It is the only way for students and society to reap the full benefits of their initial investment in a literate, educated population. Currently, 83.8 percent of children worldwide attend primary school, but the rate drops to 59.3 percent for secondary school. In sub-Saharan Africa, only 17 percent of the girls are enrolled in secondary school. A renewed push to ensure that girls worldwide have access to secondary, as well as primary education is necessary now if the investments made are to pay off. This report discusses barriers and challenges to girls, and underscores five major benefits of girls' secondary education, including: (1) Pressure on communities and countries to build more secondary schools for girls, and existence of secondary schools increases primary and middle school enrollment and quality, and parental commitment to quality education overall; (2) Social benefits to the whole society (students are less likely to engage in or become a victim of crime, youth violence or human trafficking); (3) Girls are a valuable health resource, uniquely positioned to address some of the most significant health challenges facing developing countries (infant mortality, childhood immunization and nutrition, stunting, unwanted pregnancies); (4) Mitigation of HIV and AIDS; and (5) Tool for poverty alleviation by producing high returns in terms of wage growth. Adopting the recommendations in this report (to increase access and improve retention/survival and completion rates, improve the quality by making secondary classes more relevant and more gender equitable, and increase expectations for girls' independence and success) will result in an environment that empowers girls, benefiting themselves and the world. (Contains 105 footnotes, 11 figures, and 1 table.) [This report was written with Lisa Kays and Stephanie Psaki.]