Primary education is free and compulsory for all children between the ages of 6 and 15. Secondary education consists of three years of middle school and three years of high school. In the 1997-1998 school year some 3.8 million pupils were enrolled annually in kindergarten and elementary schools and 4.7 million in middle and high schools, including vocational high schools. Private schools play an important role, especially above the primary level. The country has 297 institutions of higher education, with a total annual enrollment of 2.5 million students. The principal universities are Korea University (founded in 1905), Seoul National University (1946), Ewha Women’s University (1886), and Yonsei University (1885), all in Seoul; Chosun University (1946), in Kwangju; and Pusan National University (1946). An estimated 100 percent of the adult population of South Korea is literate—99.8 percent of the men and 99.8 percent of the women.