Single-sex education, also known as single-gender education, is the practice of conducting education where male and female students attend separate classes or in separate buildings or schools. The practice was common before the twentieth century, particularly in secondary education and higher education. Single-sex education in many cultures is advocated on the basis of tradition as well as religion, and is practiced in many parts of the world. Recently, there has been a surge of interest and establishment of single-sex schools due to educational research. Single sex education is practiced in many Muslim majority countries; while in the West it is most popular in Chile, Israel, South Korea, and English speaking countries such as Singapore, Ireland, the United Kingdom, Hong Kong, New Zealand, and Australia. In the Western world, single sex education is primarily associated with the private sector, with the public (state) sector being overwhelmingly mixed sex; while in the Muslim world the situation is the opposite: public schools are usually single sex, while many private schools are mixed sex. Motivations for single sex education range from religious ideas of sex segregation to beliefs that the sexes learn and behave differently, and, as such, they thrive in a single sex environment.
Before the 19th century, single-sex schooling was most common. During the 19th century, ideas about education have started to change: modern ideas that defined education as a right, rather than as a privilege available only to a small elite, have started to gain support in North America and Europe. As such, mass education was introduced, and more and more coeducational schools were set up. Together with mass education, the practice of coeducation was universalized in many parts. Increased secularization in the 20th century also contributed to the acceptance of mixed sex education. In 1917 coeducation was mandated in the Soviet Union. According to Cornelius Riordan, "By the end of the nineteenth century, coeducation was all but universal in American elementary and secondary public schools (see Kolesnick, 1969; Bureau of Education, 1883; Butler, 1910; Riordan, 1990). And by the end of the 20th century, this was largely true across the world. In the UK, Australia, and Ireland the tradition of single sex education remained quite strong until the 1960s. The 1960s and 1970s were a period of intense social changes, and during that era many anti-discrimination laws were passed, such as the 1972 Title IX. Wiseman (2008) shows that by 2003, only a few countries across the globe have greater than one or two percent single sex schools. But there are exceptions where the percent of single sex schools exceeds 10 percent: Belgium, Chile, Singapore, the United Kingdom, Hong Kong, Israel, New Zealand, Australia, South Korea, and most Muslim nations. Recently, however, there has been a resurgence of interest in single sex schools in modern societies across the globe, both in the public and private sector (Riordan, 2002).".