Literacy rate in Nauru, defined as "people who are currently enrolled in school and/or have reached at least grade 5 of primary education", is 96.5%, as of 2011. There are 3,190 students and 104 teachers, as of 2013. The 2011 census stated 4 percent of the population aged 15 years or older have a primary education, 91 percent have a secondary education, and 5 percent have a tertiary education. Education is based on the British system, which requires attendance from 5 to 16 years old. Students spend three years at preschool, six years of primary education, and four years of secondary school. Tertiary school is not required. An estimated 10.7 percent of the GDP was spend on education in 1999. As of 2013, there are five preschools, four primary schools, three secondary schools, and one tertiary school. The lone college, University of South Pacific, opened in the 1970s via distance courses, and in 1987 a campus was built on the island. It offers accounting, management, primary education, and English studies as majors.. How many years do students spend in tertiary school?