How does the meeting between Pa and Professor Herbert affect Dave?

The meeting between Luster Sexton and Professor Herbert begins badly; however, the results of it are positive and Dave benefits from this visit.

While Luster Sexton is angry with Dave for being late for his afternoon chores on the farm, when he hears from his son that he was the only student who had to stay after school, Luster changes his attitude. He feels that Dave was singled out because of being poor. Incensed at what he perceives as an insult to his family, Luster says,

"My boy is good as th'rest, ain't he? A bullet will make a hole in a schoolteacher same as it will anybody else."

Thus enraged, Luster accompanies Dave to school, carrying with him a gun. When he meets Professor Herbert, Luster pulls out his gun and lays it on the seat in Professor Herbert's office, frightening Herbert. However, the teacher remains calm and takes Mr. Sexton into his biology class and demonstrates how school has changed since Luster was a boy, talking to him calmly. After their exchanges, Luster tells Dave that Professor Herbert is a good man. He adds,

I'm a dead leaf, Dave. I'm behind. I don't belong here. If he'll let me I'll get a broom and we'll both sweep one hour. That pays your debt. I'll hep you pay it. I'll ast 'im and see if he won't let me hep you."

When Professor Herbert offers to cancel the debt, Luster demonstrates his integrity by saying that his family is "honest people" and they do not want something for nothing. So, he sweeps with Dave and talks to his son man-to-man; he tells Dave that he is out of touch with the times and he is not anyone important. But, he encourages Dave to be more. "Jist remember, Dave, to pay your debts and be honest."

Certainly, Luster Sexton has changed his perspectives about school and about his son as he hopes Dave will achieve more than he has. Moreover, he demonstrates respect for his son and treats him as a man, rather than as a boy.