Little Johnny’s father glared …

Little Johnny’s father glared at the school report and asked “Why did you fail maths?”
“On Monday, the teacher said six fours make twenty-four. Then on Tuesday, she said twelve twos make twenty-four. And on Wednesday, she said three eights make twenty-four.”
“Right,” said his father.”So?”
“If she can’t make up her mind, how am I ever going to get anything right?”