Most people age 15 and older in Tajikistan can read and write, a result of the Soviet system of free and universal education. Until the 1920s, when the Soviet authorities introduced secular (nonreligious) education, the main education centers were Muslim madrasas (religious schools). In principle, a general education involving the completion of seven grades is compulsory for all children. However, the government has not maintained adequate state funding for schools due to the country’s economic and political instability. Institutions of higher education in Tajikistan include the Tajik State University, the Tajik Agricultural University, and the Tajik Technical University, all located in Dushanbe. The Tajik Academy of Sciences, also located in Dushanbe, is an important research institute.