Why is Dave running late returning home from school?

While he was at school on a field trip, Dave and five of his friends chased a lizard up a cherry tree. Under the strain of their collective weight, the cherry tree split and was ruined. The tree belonged to a Mr. Crabtree and he had been plowing at the time and caught them in the act of destroying the tree. Mr. Crabtree decided to make each boy pay one dollar to cover the cost of the tree. Dave doesn't have a dollar, so Professor Herbert says he must stay after school two hours on two consecutive days. At twenty-five cents an hour, he will then be paid up. Dave has farm work to do at home. He knows his father will be mad with him for being late. He even fears that he will be whipped for being late. He explains to Professor Herbert that his father is a bit old fashioned in this way: 

"You don't know my father," I says to Professor Herbert. "He might be called a little old-fashioned. He makes us mind him until we're twenty-one years old. He believes: 'If you spare the rod you spoil the child.' I'll never be able to make him understand about the cherry tree. I'm the first of my people to go to high school." 

So, Dave hurries home because the later he is, the angrier his father will be. Having stayed two hours after school, he is late and his father is angry. This instigates the confrontation between his father and Professor Herbert the following day.