Thanks for all the responses. I was just curious where other parents stand on this. I'm glad to see that I'm not the only one who thinks it's wrong saying you're 13 when you're not. I think I'm going to keep holding my DD off on signing up for Facebook. She's already been asking for about 6 months.
Thanks Carnie for posting that letter from the principal, that was very helpful.
If it would help you could do what we did. A few months ago (when DS was still 12) he asked for a FB page. (DH and I have had ours for abour 2 years.) DH sat down with DS and started to fill out the info to get a FB page. He put in his real birthday and he was not allowed. DS knows it's not okay to lie so he didn't ask again until today, when he turned 13. We have already talked to him about being responsible and he is a good kid. We will monitor his page and make sure he handles it well.
He doesn't want on FB anymore.. 
with privacy settings at the highest possible! They have 6 friends... me dad uncle aunt and 2 kids down the street.. They play happy pets, happy aquarium and farmville... 9 yr old doesn't want though 
, but my DD is a little immature and occasionally has diarrhea of the mouth
. It's bad enough to hear some of the things she says, I certainly don't want it out there forever in cyberspace.