Why do you think they skipped that part? This is a subject of interest to me as well. Maybe thread-worthy.
Ah, that thread would be doomed for a lock.
If they could have told us the founders were all Southern Baptists and gotten away with it, they would have. Pretty big "America is only great because of Christianity" attitude around.
There were some exceptions, like my 8th-grape AP American History teacher, but in general schools don't want you to know that the Heroes of American History questioned the popular beliefs of the time, because they are afraid you'll start doing it too.