While not "Bronze Age" (They did, in fact, smelt bronze, but Mesoamerican, and really all non-European and Near-East societies don't really fit into the "3 Ages" system/model, and were more complex then either a "Bronze Age" or the more common "Stone Age" label would imply); you might find this comment by /u/400-rabbits and the various reply chains and further comments given by him, to answer your question in terms social mobility in Aztec society.