I’m with beatus, it doesn’t say how old the “kids” are, only implying that the submitter is a teacher (though I hope they took points off for “killing to many people”). These could easily be Juniors or Seniors in High School. So I’m guessing not fake
I can’t see any teacher doing an exercise as silly and puerile as getting kids to write letters to celebrities when the kids are anything over about 8 or 9. The only logical explanation is that these kids are the funniest Special Ed. class ever.