This is actually a very interesting question because the novel as a whole seems to stress the importance of education through focusing on the way in which Mary Call Luther and her family manage to self-educate themselves and show themselves to be so resilient and able to adapt to the very harsh circumstances that they find themelves in. They do this through providing for themselves through becoming "wildcrafters," people who find, gather and sell various plants that can be used for medicinal purposes and grow wild in the mountains.
The fact that they teach themselves this craft and learn how to haggle and sell stresses how important education is, but not simply education in the traditional sense. Mary Call Luther and her family manage to achieve this without any formal training, and thus represent a powerful example of the ability of humans to educate themselves. The novel as a whole, and especially the character of Mary Call, is a powerful testament to the indomitable nature of the human spirit, which, in the face of adversity, has the ability to persevere until its reaches its objective.