The University of Havana was founded in 1728 and there are a number of other well-established colleges and universities. In 1957, just before Castro came to power, the literacy rate was fourth in the region at almost 80% according to the United Nations, higher than in Spain. Castro created an entirely state-operated system and banned private institutions. School attendance is compulsory from ages six to the end of basic secondary education (normally at age 15), and all students, regardless of age or gender, wear school uniforms with the color denoting grade level. Primary education lasts for six years, secondary education is divided into basic and pre-university education. Cuba's literacy rate of 99.8 percent is the tenth-highest globally, due largely to the provision of free education at every level. Cuba's high school graduation rate is 94 percent.