And if he doesn't, you'd better tell him now because you seriously don't want him to be the last one on the playground to find out. That wouldn't be pretty :-p
Agree with the others. Superfudge is fine. Even if your son does believe in Santa at this age (he may not, some children hide the fact that they “know” from their parents), I can’t imagine him entering 5th grade still believing.
I can assure you that many of the other children in the class are innocent in their belief in Santa Claus, as well, and I'm not the only parent with this concern.
Children in the class who may not believe may probably be instructed not to unravel this part of childhood for others, but you know how that goes.
I suspect that my son may realize that Santa is really the work and love of his parents, but I'm not sure? Regardless, I'd rather the truth be revealed by myself, rather than by the teacher.