I think that this is a hoax. Why? Well, unless two groups of kids, unbeknownst to each other, have come up with the same ideas to bully the victims (always a possibility), the writer of the letter is merely repeating what he (no, it's not a she) saw in the media. (BBC does not mention the specifics of the bullying methods that have been quoted in the Japanese media.)
The real tragedy is that the education authorities have no clue as to what's going on out there, in the classrooms and schoolyards. Why else would they have to take it so seriously?