For a guy who never learned to read or write, Papa sure puts a lot of stock in education. He is absolutely adamant that Rob should continue in school and "get all the teaching [he] can hold" (12.100). Papa knows that many people see him as less of a person simply because he's not educated, and he doesn't want that to happen to Rob. But at the same time, Papa also recognizes that there are sources of knowledge beyond those of a traditional education—this "earthy reason," as he calls it, is just as important to a rounded life. And as much as we love our books, we have to say we totally agree.
While Papa clearly values education, the book shows that the virtues Papa himself has—determination, honesty, a belief in hard work—are ultimately more important than book learning.
Papa sees education as Rob's path out of poverty, which is why he so wants Rob to stay in school.