Um....my 7th grader still does, as does her 5th grade brother. (and neither are special needs) ;)
Not being around other children in a classroom setting, they have not had the opportunity to have their 'bubble burst'. I assume that she will figure it out soon, but right now she still has that childlike innocence, and I'm not going to strip that away from her.
I will say though that Santa is not a big part of our Christmas celebration.
Santa leaves each of our kids one gift, and we have never really gotten into the mythology of him all that much, as we prefer to focus on the true meaning of Christmas - the birth of Christ. Still the kids mail a letter to Santa each year (which is answered...by local postal workers) and they get their one gift... so the 'magic' stays alive.