"Why don't you do your math group work with George any more?" Pete's math teacher asked him.
"Would you want to work on math with someone who puts down the wrong answers and even fakes their work when you aren't watching? replied Pete.
"No," Pete's teacher replied, "I certainly wouldn't."
"Neither will George."
Source: J. Braude's Treasury of Wit and Humor, 1964 (variation of joke #375)