Classical latin education ftw. But fr that's the best odds you're going to get. Classical Latin is often taught as it was in the late republic/Julian dynasty, unless you got ecclesiastical Latin in which case, you've got a decent area and you better hope you're in the middle ages in europe and want to talk to the clergy.

But yeah, in general ancient languages as we currently understand them are really the languages of the educated, elites, merchants, and clergy. You have exceptions for highly literate societies like Rome where we have plenty of graffiti teaching us vulgar words like irrumatio. But for the most part writing was for records and official communication for a long time.