Education in Sudan is free and compulsory for children aged 6 to 13 years, although more than 40% of children do not go to schools due to the economic situation. Environmental and social factors also increase the difficulty of getting to school, especially for girls. Primary education consists of eight years, followed by three years of secondary education. The former educational ladder 6 + 3 + 3 was changed in 1990. The primary language at all levels is Arabic. Schools are concentrated in urban areas; many in the west have been damaged or destroyed by years of civil war. In 2001 the World Bank estimated that primary enrollment was 46 percent of eligible pupils and 21 percent of secondary students. Enrollment varies widely, falling below 20 percent in some provinces. The literacy rate is 70.2% of total population, male: 79.6%, female: 60.8%.