The other two answers are excellent: only a human can teach anyone how to be a human, and AIs are structurally incapable of understanding any concept sufficiently to teach it.
I might further add: the current structure of AI as a wholly for-profit enterprise adds a level of cynicism and a susceptibility to corruption that even a for-profit human educator is not subject to; that is to say, do we want any corporation (really, any single entity) to be responsible, not only for the structure of education, but for its entire expression?
Even if a hypothetical perfect AI were completely benevolent, and owned by the people, it would still represent a bottleneck of thought and idea that would heterogenize our society. But we don't live in that world, so it's almost a certainty that education would be for sale to the highest bidder. You think historical revisionism is bad now? What if BMW could pay OpenAI to downplay the role of Germany in World War II?