forced marriages; early pregnancy; prejudice based on gender stereotypes at home, at school and in the community; violence on the way to school, or in and around schools; long distances to schools; vulnerability to the HIV epidemic; school fees, which often lead to parents sending only their sons to school; lack of gender sensitive approaches and materials in classrooms. Sex segregation Sex segregation is the physical, legal, and cultural separation of people according to their biological sex. It is practiced in many societies, especially starting when children attain puberty. In certain circumstances, sex segregation is controversial. Some critics contend that it is a violation of capabilities and human rights and can create economic inefficiencies and discrimination, while some supporters argue that it is central to certain religious laws and social and cultural histories and traditions.Nussbaum, Martha C. 2003. "Women's Education: A Global Challenge." "Signs: Journal of Women in Culture and Society" 29(2): 325–355 Purdah is a religious and social practice of female seclusion prevalent among some Muslim and Hindu communities in South Asia. It takes two forms: physical segregation of the sexes and the requirement that women cover almost entirely their bodies. The ages from which this practice is enforced vary by community. Such practices are most common in cultures where the concept of family honor is very strong. In cultures where sex segregation is common, the predominant form of education in single sex education. Violence against girls In many parts of the world, girls are at risk of specific forms of violence and abuse, such as sex-selective abortion, female genital mutilation, child marriage, child sexual abuse, honor killings. In parts of the world, especially in East Asia, South Asia and some Western countries' girls are sometimes seen as unwanted; in some cases, girls are selectively aborted, abused, mistreated or abandoned by their parents or relatives.A. Gettis, J. Getis, and J. D. Fellmann (2004). Introduction to Geography, Ninth Edition. New York: McGraw-Hill. pp. 200. In China, boys exceed girls by more than 30 million, suggesting over a million excess boys are born every year than expected for normal human sex ratio at birth. In India, scholars estimate from boy to girl ratio at birth that sex-selective abortions cause a loss of about 1.5%, or 100,000 female births per year. Abnormal boy to girl ratio at birth is also seen in Georgia, Azerbaijan and Armenia, suggesting possible sex-selective abortions against girls.