Saying a group isn't 'well-educated' carries a negative valence in English, BTW, so I'd stay away from that. But the original question is valid.
They have shown people in nonliterate cultures have better mnemonic ability; ancient Hellenic poets would memorize the Iliad, Odyssey, etc. So you do lose something when you invent writing.
There are all kinds of debates over the term 'shamanism' (the word refers originally only to the spiritual practitioners of the indigenous peoples of Northern Europe and Siberia), but anthropologically, there does seem to be a move from interacting directly with spirits to a sort of priesthood that has a religious bureaucracy as cultures become more stationary and involve larger groups. One step of the process of moving from nomadic bands and tribes through chiefdoms to states often involves the development of a written language (helps to keep accounts and it's hard to keep big bulky books with you when you're moving around all the time), so there is some correlation there.