What is significant about Junior speaking up in class?

For the first time in his life, Junior begins to feel more intelligent than other kids at the white school. Junior speaks up in Mr. Dodge's geology class. He corrects Mr. Dodge about Petrified wood not being actual would: it is only minerals in the shape of wood. Mr. Dodge is not amused at being corrected but sees Junior's intelligence. Other kids, like Gordy, also take note of Junior's knowledge.