Education in Portugal is free and compulsory until the age of 18, when students usually complete their year 12. However, only one of those requirements is necessary. The education is regulated by the State through the Ministry of Education. There is a system of public education and also many private schools at all levels of education. The first Portuguese medieval universities, such as the University of Coimbra, were created in the 13th century, and the national higher education system is fully integrated into the European Higher Education Area. The basic literacy rate of the Portuguese population is 99.44 (99.48% male, 99.38% female, aged 15–24). According to INE (Portuguese Institute for National Statistics), only 3.7 million Portuguese workers (67% of the working active population) completed basic education (81% of the working population attained the lower basic level of education and 12% attained the intermediate level of education). According to the Programme for International Student Assessment (PISA) 2015, the average Portuguese 15-year-old student, when rated in terms of reading literacy, mathematics and science knowledge, is placed significantly above the OECD's average, at a similar level as those students from Norway, Poland, Denmark and Belgium, with 501 points (493 is the average). The PISA results of the Portuguese students have been continuously improving, surpassing those of a number of other highly developed western countries like the US, Austria, France and Sweden. In the beginnings of the Portuguese nationality, the Christian clergy was the main player in the educational endeavour. Portuguese universities have existed since 1290. Within the scope of the Portuguese Empire, the Portuguese founded in 1792 the oldest engineering school of Latin America (the Real Academia de Artilharia, Fortificação e Desenho), as well as the oldest medical college of Asia (the Goa Medical College) in 1842. However, by the end of the 19th century the illiteracy rate was over 80 percent and higher education was reserved for a small percentage of the population.