We know that one of the most effective attractors of colonial America was the freedom of religious expression. Puritans, Quakers, Calvinists, you name it - all were welcome. This doesn't really appear to have been tested to a great extent by those of Jewish and Islamic faiths, but there does not seem to be any record of persecution of these groups, so it would seem the only serious "religious" persecution was centered around the Salem witch trials (which were actually probably politically and civilly-motivated, but spun to make it an issue of witchcraft and Satanic dealings to get the public behind it).
In any case, as my wife and I prepare my own children for their own formal religious education (we're Catholic), and as I continue my philosophical and religious explorations throughout my adult life, I'm wondering what would happen if my kids said "no" to church. Would they have the protection of the Constitution on their side? What would the Supreme Court hold, assuming the sensational case would eventually ascend to their wise judgement? As their parents, we are responsible for their physical, educational, and moral upbringing, and though moral behavior exists with or without religion, the two are frequent companions.
So it would seem that it would be well within our parental rights, even responsibilities, to expose them to, or force upon them, whatever religious indoctrination that we deem appropriate. If this seems like a harmless supposition (after all, Catholics as an organization haven't brutally harmed other groups en masse in CENTURIES, or at least decades, not including defenseless child victims of sexually abusive clergy), then take it a giant step further: what if the parents were not Christian? What if they weren't monotheistic? What if, even more shocking, they were Satanists? Would you then afford those parents the same "religious freedom" protection to force that indoctrination onto their 5, 6, or 7 year old children? Of course not. But what about a gray area that exemplifies the non-black and white term perfectly for most of us, since we don't really know anything about it: what about Scientology? Many people think it's a bit nutty, maybe even financially harmful to its adherents, but not associated with illegal physical harm or anything of that nature. Are those parents allowed to force their beliefs on their children, against their children's will?
Fortunately, my wife and I share a strong religious faith and it is very appealing to our children at this point in their lives, so there are no conflicts. But what if they refused to believe? What if they refused to even enter the Church? Who could they turn to for help or protection, and what would that authority say to them? What would our courts say?