A mother walked into her son’s room and said cheerfully, "Time to go to truck driving school."

The son buried his head in the covers and groaned, "I don’t want to go to truck driving school."

"Come on, now, you have to go."

"I don’t want to go."

"You have to."

"I hate it there. It’s like a jungle. One fight after another. The students hate me. They threaten me a hundred times a day!"

"You still have to go."

"Why?"

"Because you’re the trainer."