The educational system of the United Arab Emirates has burgeoned since 1971. Education in the six northern emirates, formerly financed and administered by Kuwait, has been managed by the UAE Ministry of Education since 1972. Education is compulsory for six years at the primary level, from age six, and is free to all UAE citizens, as are school uniforms, books, equipment, and transportation. Arabic is a compulsory subject, and segregation of classes by sex is required. The system remains concentrated at the primary level. At the secondary level, children go through six years of education in two stages. In 1997, there were 259,509 pupils and 16,148 teachers at the primary level. Student-to-teacher ratio stood at 16 to 1. In the same year, secondary schools had 180,764 pupils and approximately 11,000 teachers. As of 1999, 78 % of primary-school-age children were enrolled in school, while 68% of those eligible attended secondary school. United Arab Emirates University is at Al 'Ayn. In 1997, all higher-level institutions had 16,213 students. Approximately 16.7% of the central government budget was allocated to education in the latter part of the 1990s. As of 1999, public expenditure on education was estimated at 1.9% of GDP. For the year 2000, adult illiteracy rates were estimated at 23.5% (males, 24.8%; females, 20.5%).