Education is free up to college level and is compulsory between the ages of 5 and 12. The educational system is based largely in the British school system. Projected adult illiteracy rates for the year 2000 stand at 15.7% (male, 12.3%; female, 19.0%). In 1997, an estimated 283 primary schools had 127,109 pupils and 6,434 teachers. General secondary schools had a total of 93,839 pupils and 4,710 teachers in the same year. The pupil-teacher ratio at the primary level was 26 to 1 in 1999. In the same year, 94% of primary-school-age children were enrolled in school, while 73% of those eligible attended secondary school. Postsecondary institutions include the University of Mauritius, the Mauritius College of the Air, and the Mahatma Gandhi Institute. In 1997–98, all institutions of higher learning combined had 6,419 pupils, 50% of which were female. Many university students study in Europe, India, Australia, and the United States. As of 1999, public expenditure on education was estimated at4.2% of GDP.