schools. ISC defines an 'international school' in the following terms "ISC includes an international school if the school delivers a curriculum to any combination of pre-school, primary or secondary students, wholly or partly in English outside an English-speaking country, or if a school in a country where English is one of the official languages, offers an English-medium curriculum other than the country's national curriculum and is international in its orientation." This definition is used by publications including The Economist. Educational years School years The table below describes the most common patterns for schooling in the state sector: History of education In central Mexico, the history of education stretches back to the Prehispanic era, with the education of Nahuas in schools for elites and commoners. A formal system of writing was created in various parts of central and southern Mexico, with trained experts in its practice. After the Spanish conquest of the Aztec Empire, friars embarked on a widespread program of evangelization of Christianity. In the colonial era, schooling of elite men of European descent was established under the auspices of the Catholic Church. Liberals' attempts to separate church and state in post-independence Mexico included removal of the Catholic Church from education. Education remains an important aspect of Mexican institutional and cultural life, and conflicts continue about how it should be conducted. The history of education in Mexico gives insight into the larger history of the nation. Education in Mesoamerica Before the Spanish In central Mexico in the cultural area known as Mesoamerica, the Aztecs set up schools called calmecac for the training of warriors and schools for the training of priests, called cuicacalli. An early post-conquest manuscript prepared by native scribes for the viceroy of Mexico, Codex Mendoza shows these two types of schools. Aztec religion was highly complex and priests held a higher status, so that the creation of schools to train them in ritual and other aspects of religion was important. Overseeing an expansionist empire, Aztec rulers needed trained warriors, so that the creation of formal schools for their training was as important. Colonial-era education, 1521–1821 Education of the indigenous in Central Mexico The Spanish Crown made a significant commitment to education in colonial New Spain. The first efforts of schooling in Mexico were friars' evangelization of indigenous populations. "Educating the native population was a crucial justification of the colonizing enterprise, and that criollo (Spanish American) culture was