For over a hundred years before the Conquest, education in Tenochtitlan was compulsory for all male children. They studied eitherin the specialized calmecac, of which there were at least six in the city, or the telpochcalli, which were attended by the great majority. The students in the calmecac were taught to read and interpret the codices and calendars; they also studied the tribe's history and traditions, and memorized the sacred hymns and other texts. So much emphasis was placed on accurate memorization that after the Conquest it was possible to record many poems and traditions that would otherwise have been lost forever. Most of the students in the calmecac were sons of nobles or priests, but there is evidence that children of humble origin were sometimes admitted if they showed exceptional aptitude.
Almost every sector or clan in Tenochtitlan had its own telpochcalli, dedicated to the god Tezcatlipoca. The students were taught the fundamentals of religion and ethics, and were also trained inthe arts of war. In comparison with the calmecac, the telpochcalli offered a more basic and practical education. As we have said, every boy had to attend one of these two types of schools, and every father had to make a solemn vow, on the birth of a son, that he would send the boy to school when he reached the proper age, which seems to have fluctuated between six and nine years.