His mark was so bad, his teacher called home to have a word with his dad.
When he returned home that afternoon, his father was standing crossly in the doorway. “Why did you fail your math test?” he asked.
Little Johnny shrugged and said: “My teacher isn’t very good.”

Johnny’s father was astonished by his excuse and urged him to expand. “Well, on Monday, my teacher said 3+5 = 8.”

“So?” his father replied.
“Then on Tuesday, she told us 4+4 = 8, and on Wednesday she said 6+2 = 8,” explained the child.,“If she doesn’t know what equals eight, how am I supposed to know the right answer?”