text: The sons of commoners were trained in the Tēlpochcalli  "house of youth". Once a boy reached the age of ten, a section of hair on the back of his head was grown long to indicate that he had not yet taken captives in war. At age fifteen, the father of the boy handed the responsibility of training to the telpochcalli, who would then train the boy to become a warrior. The telpochcalli was accountable for the training of approximately 419 to 559 youths between the ages of fifteen and twenty years old. While the boys were in training, they were given basic duties, such as cleaning the house and making fires. The youth were tested to determine how fit they would be for battle by accompanying their leaders on campaigns as shield-bearers. War captains and veteran warriors had the role of training the boys how to handle their weapons. This generally included showing them how to hold a shield, how to hold a sword, how to shoot arrows from a bow and how to throw darts with an atlatl. Boys in training were only considered real men when they captured their first warrior.
  Sons of the nobles were trained at the calmecac  ("lineage house") and received sophisticated training in warfare from the most experienced warriors in the army, as well as in general courtly subjects such as astronomy, calendrics, rhetorics, poetry and religion. The calmecac were attached to temples as a dedication to patron gods. For example, the calmecac in the main ceremonial complex of Tenochtitlan was dedicated to the god Quetzalcoatl. Although there is uncertainty about the exact ages that boys entered into the calmecac, according to evidence that recorded the king's sons entering at the age of five and sons of other nobles entering between the ages of six and thirteen, it seems that youth began their training here at a younger age than those in the telpochcalli did.