Dead Man’s Planet by William Morrison

Outside the ship, it was the sun that blazed angrily. Inside, it was Sam Wilson’s temper. “Study your lessons,” he snarled, with a savageness that surprised himself, “or I’ll never let you set foot on this planet at all.”

“Okay, Pop,” said Mark, a little white around the nostrils. He looked old for so young a kid. “I didn’t mean anything wrong.”

“I don’t care what you meant. You do as you’re told.”

In the quiet that followed, broken only by the hum of the arithmetic-tape, Sam wondered at himself. As kids went, Mark had never been a nuisance. Certainly Rhoda had never had any trouble with him. But Rhoda had been altogether different. Sam was tough and he had always got a sense of satisfaction out of knowing that he was hard-boiled. Or at least that was once true. Rhoda had been sweet, gentle....

He aroused himself from thoughts of her by calling, “Mark!”

“Yes, Pop?”

His voice had been harsher than he had intended. Over the past few weeks he seemed gradually to have been losing control of it. Now, although he was going to do his son a favor, he sounded like a slavemaster threatening a beating. “You can shut off your arithmetic lesson. We’re going out.”

“But didn’t you want me—”

“I changed my mind.”