A popular school joke has a teacher discovering that one student had copied from another. All of the answers were identical except one, where one student wrote “I don’t know” and the other wrote “Me, neither.”
 
The joke has been cited in print since at least 1951.
 
         
18 February 1951, The Times-Picayune.New Orleans States (New Orleans, LA), “Bright Talk,” Dixie (Roto Magazine), pg. 18, col. 4:
Test for Two
A NEIGHBOR wasn’t any too pleased when her son, Jimmy brought home an “F” on his report card. She immediately went up to see the teacher for an explanation.
 
“Well,” said the teacher, “Jimmy copied from the boy next to him on his test paper.”
 
“Do you have any proof?” asked the mother.
 
“I have some pretty good evidence,” she explained pleasantly. “It seems that Jimmy had identical answers with the boy next to him on every question but the last. On that one, the other boy had written, “I don’t know,’ and Jimmy had written, ‘Me neither.’”
—Miss Vivian Dupree
P. O. Box 234, Marksville, La.
       
Google Books
The American Mercury
Volume 84
1957
Pg. 34:
Young Johnnie took a test in school. He sat next to his pal, Ronald, who was also the smartest boy in the class. When they handed in their papers, Johnnie was sure he would get a good grade because he had copied all the answers from his friend.
 
Great was his surprise and dismay next day when the teacher read out the grades giving Johnnie a zero, while his friend received a 90. After class, Johnnie complained to the teacher.
 
“Ronald and I studied together for the test,” he protested, “so I’m sure our answers were exactly alike.”
 
“Not quite,” explained the teacher. “Out of ten questions, you answered nine alike. For his tenth answer, Ronald wrote, ‘I don’t know the answer to this question.’ You put, ‘Me neither.’ ” — EDDY ANDERSON
 
20 August 1983, Iowa City (IA) Press-Citizen, “Here’s proof you aren’t reading this” by David Kanellis, pg. 4A, col. 3:
I told them the odds were pretty high against these identical answers coming up by chance alone, In other words I accused one of the guys of copying.
 
The evidence was pretty clear, too. Where the one kid wrote “I don’t know,” in answer to the 20th question, the other one wrote “Me neither.”
   
Google Books
Over 1500 Fantastic Jokes
By Guy Campbell, Mark Devins, Paul Moran and Simon Ecob
London, UK: Dean
2002
Pg. 208:
Teacher: Samantha, you copied these answers from Monica, didn’t you?
Samantha: What makes you say that?
Teacher: Because her answer to question 5 is “I don’t know,” and yours is “Me neither”.
 
Twitter
Blank Trails
@Blanktrails
Teacher:u copied 4m Fred’s exam paper didn’t u? |
Pupil: How did u know? |
T:Fred’s paper says “I don’t know” and u have put “Me, neither”!
3:30 AM - 26 Dec 2009
 
Twitter
lorraine Jo King
@LahLahBean
#jokes
Teacher: Jeff, have you been copying Johnny’s test again?
Jeff: Yes, but how did you know?
Teacher: On question 1, Johnny put down “I don’t know”.
And you put down “Me neither”.
8:07 AM - 20 Jul 2018