The adult illiteracy rate in 1995 was estimated at 0.4% (males, 0.3%; females, 0.5%). The educational system was not developed until after the 1920s when the country came under Soviet control. In 1996, 473,077 students were enrolled in 1,885 primary schools, with 24,086 teachers. In the same year, secondary schools had 530,854 students and 42,286 teachers. The pupilteacher ratio at the primary level was 24 to 1 in 1999. In the same year, 82% of primary-school-age children were enrolled in school. In 1996, there were 49,744 students enrolled and 3,691 teaching staff employed at institutions of higher learning, including the State University of Kyrgyzstan. As of 1999, public expenditure on education was estimated at 5.4% of GDP.