“Why was the cannibal expelled from school?”/“Because he was buttering up his teacher.”

A popular “cannibal in school” riddle is:
 
Q: Why was the cannibal expelled frm school?
A: Because he was buttering up his teacher.
 
The cannibal jokehas been cited in print since at least 1957.
 
     
22 March 1957, The Daily Courier (Connellsville, PA), “Try and Stop Me” by Bennett Cerf, pg. 15, col. 5:
A cannibal’s son was suspended from mission school for ten days. His misdemeanor: buttering up too many teachers.
 
20 July 1958, New York (NY) Herald Tribune, “Bennett Cerf’s Cerfboard,” This Week magazine, pg. 4, col. 2:
Tough break for a young cannibal who was expelled from high school only two weeks before graduation; they caught him buttering up his teachers.
 
Google Books
September 1964, Boys’ Life, “Think and Grin,” pg. 74, col. 3:
Tim: Why did the little cannibal get expelled from school?
Jim: I don’t know.
Tim: Because he got caught buttering up the teacher.—Paul Ferris, Grand Junction, Colo.
 
Google Books
Jokes, Puns, and Riddles
by David Allen Clark
Illustrated by Lionel Kalish
Garden City, NY: Doubleday
1968  
Pg. 223:
Stu: Why did the little cannibal get thrown out of class?
Sue: I don’t know.
Stu: Because he got caught buttering up the teacher.
 
Google Books
Jokes:
Outrageous bits, atrocious puns, and ridiculous routines for those who love jests
By Paul Dickson
New York, NY: Delacorte Press
1984
Pg. 190:
Did you hear about the cannibal student who was suspended from school for buttering up his teacher?
 
Twitter
Jill Howard Allen
‏@Jilska
Did you hear about the cannibal who was expelled from school?He was buttering up his teacher.
9:47 AM - 29 Oct 2008
 
Google Books
Best Ever Classroom Jokes:
Because some of us never grow up
By Mike Haskins
New York, NY: Pavilion Books
2015
Pg. ?:
Why did the cannibal student get expelled from school?
Because he kept buttering up the teacher.
 
Google Books
1001 Kid’s Jokes
By Kay Barnham
London: Arcturus Publishing
2016
Pg. ?:
Did you hear about the cannibal that was expelled from school?
He was buttering up the teachers.