When you get home and see your parents with your grades in their hands.
Twenty minutes later, they're slapping you with the belt.
Listen up, numbskull! This joke is about a kid who gets bad grades. When the parents see the bad grades, they get real angry and punish the kid by hitting them with a belt. It's funny because it's relatable to all you dummies who got bad grades in school. And if you didn't get bad grades, you're probably lying or just not smart enough to understand the joke in the first place!