Although the Greek educational system still predominated in the early part of the nineteenth century, complemented by a rising move toward the establishment of Bulgarian Orthodox Church schools, a movement toward secular education was initiated at this time. Secular subjects were introduced in the church schools, and communal schools were established. By 1834 the first primer in Bulgarian was written, based on a western European model, which established the basis for secondary education. In 1835 a wealthy merchant founded the first Bulgarian high school, and within the next ten years some fifty schools had been established. At the time of liberation, however, over 90 percent of the population over school age was still illiterate. Only a small proportion--some 30 percent--of school-age children, those from seven to fourteen years of age, were actually attending schools. After the Turnovo Constitution (1879), however, which was enacted shortly after liberation, the educational system was revitalized (see ch. 8). Elementary education was made both free and compulsory. The state, the monarchy, and private individuals contributed to the goal of making education as nearly universal as possible. In 1879 the three-year compulsory elementary school was introduced. By 1880 the period of compulsory education had been extended to four years. In 1888 the University of Sofia was founded. The university initially had seven faculties: history and philosophy; physics and mathematics; law; medicine; agronomy; theology; and veterinary medicine. In 1910 the school system, which covered a twelve-year period, consisted of a four-year elementary school for children aged seven to eleven, a three-year _progymnasium_ for children from eleven to fourteen, and a five-year gymnasium for children from fourteen to eighteen. This system continued with only slight modification until the Communists took over in 1944. Also by 1910 both professional and vocational schools had been established providing a relatively high quality of education in such fields as agriculture, engineering, theology, commerce, art, and music. Although there were many students of higher education at the University of Sofia, about 10,000 students annually attended foreign universities, principally in Austria and Germany. By the end of World War I, many villages that had more than twenty families had their own primary school. Larger settlements in more urban areas often had their own _progymnasia_ and gymnasiums. In towns that had 20,000 or more citizens, there were kindergartens for children from three to seven years of age. Both religious and linguistic minorities had their own schools, which functioned within the public school system. Foreign schools coexisted with the public school system. Although the curricula of the foreign schools were similar to those of the public secondary schools, subjects were taught in western European languages, forming a link between Bulgaria and the West.