Also, you say you're writing a letter to the school board... what school board? If you got the state wrong, then chances are you aren't sending the letter to the proper school board. I'd really like to know what you saw (a city, a school name) to make you think they were from Michigan.
We Lansing folk would appreciate it if (1) you would apologize for publicly and incorrectly criticizing our students and (2) stop.
If the letter was sent, and the Super knows there have been no overnight trips, there is no harm or foul, as they will most likely assume the letter was sent by mistake.
Not to mention, that the OP was told that's where the students were from. "Politely" trolling a site is still just that. Trolling.
DCGirl, while you might need to do a little more investigating to find out who you need to write, I think you should go through with the letter, and Eviltrish says mention the "backlash" from "newsmen" about your post here, though, that would be bad.