Oxford was teaching before the Aztec Empire existed

Teaching was already going on at the University of Oxford in 1096. Tenochtitlan, the capital of the Aztec Empire, was not founded until 1325.

Put another way: when the Aztecs were beginning to build their empire on the lake, Oxford had been holding classes for more than two centuries.

History is rarely a tidy queue: many things we imagine to be worlds apart were happening at the same time.