I'm concerned about this also. It's a few years until my son will be in school, but I still think about it. I was baptised Catholic, my son was baptised Greek Orthodox like his father. I don't believe in any of the Catholic ideas, in fact I'd probably classify myself as an Atheist. However I really want DS to go to a private school, but I don't want all these ideas forced upon him.
On the other hand.. perhaps if we view it as him just learning about the religion, rather than adopting it, it won't be as hard?