I'm too old to know the slang now :(

Student: OHMYGOD, Mrs. S, [student #2] said that 4 times 8 is 28, can I neck him?
Me: Can you what?
Student: Neck him.  You know, because he thought that 4 times 8 is 28.
Me: What do you mean, "neck him"?
Student: This: *karate chops the neck of the boy next to him*
Me: Ohhh...you guys realize "necking" is a word for making out, right?
Students eyes widen...
Student #2: OHMYGOD, can I please go wash my mouth out at the water fountain?!?!