I heard this as a kid, there are many variations of it all over the web:
Johnny Fucker's father was a rich and successful, and politically connected man, and wanted nothing but the best for his only son, Johnny so he sent him to public high school. Johnny was a troublemaker, went to the principal's office on a regular basis, and one day he got detention, and he was the only student who did that day. The teacher watching him was Ms. Thomas, a 26 year old, fresh out of college, starting a lifelong career as an English teacher. Johnny rose his hand, the teacher replied, "Yes, Johnny?" Johnny replies, "Teacher, can you take off your shirt." The teacher replies, "No, Johnny!" Johnny replies, "If you don't I'll tell my mom my mom will tell my dad then my dad will tell the principal and then you'll get fired." So, the teacher ponders the question knowing how powerful Johnny's father is, and she doesn't want to get into trouble with the principal in her new job of a long career so she takes off her shirt. Johnny is smirking, and playing with his desk then he asks the teacher, "Ms. Thomas, can you take off your skirt?" The teacher thinks that's just going too far and Johnny replies, "If you don't, I'll tell my mom, my mom will tell my dad and my dad will tell the principal and you'll get fired." She ponders this and then reluctantly agrees and removes her skirt.
So, Johnny is messing with his desk again, looking lustfully at the teacher, and he says, "Ms. Thomas could you remove the rest of your clothes?" and the teacher is just flabbergasted and she begins to yell at how naughty Johnny is and Johnny replies, "If you don't I'll tell my mom my mom will tell my dad and my dad will tell the principal and you'll be fired." In anger she agrees but with some resistance.
Awhile later Johnny asks, "Ms. Thomas, can I fuck you?" and she says a resounding "NO!", and Johnny replies, "If you don't I'll tell..." Ms. Thomas interrupts Johnny and says, "...I know, you'll tell your mom, your mom will tell your dad, your dad will tell the principal and then I'll be fired." She thinks about it for a second and then says, "Okay, Johnny.". A few minutes go by and the classroom door opens and it's the principal! He sees Johnny on top of Ms. Thomas and he yells, "JOHNNY FUCKER!" and Johnny replies, "I AM! I AM!".