My atheist colleague at work today said something interesting today. He said, "I have a beef. I don't know how they do things these days, but when I was growing up, they acted like there were only Catholics. And where I grew up, it was very monoculture--bunch of white French Canadians. It wasn't until I grew up that I started hearing about this Jewish thing, then that Hindu thing, and so on, all these other things. Doesn't seem right to me to do that to kids..."
Okay, so it's not an exact quote, but that's the basic gist of it. The beef, I guess, is another way of stating the common atheist complaint that religious parents brainwash their children. I'm sure that some do, to an extent, though I don't agree with the characterization of teaching your children your beliefs, in itself, as brainwashing (at all).
In any case, I'm not commenting on his particular experience because I just don't know, but it does highlight a potential problem for religious parents (and religious educators). The problem is not so much that we need to worry about brainwashing, per se, but rather that we need to guard against leaving our children so ill equipped that when they do get more exposure to the broader world and its many different philosophies and ideologies. We need to ensure that they have enough grounding in the faith that they are not swept away in whatever wind happens to catch their sails.
If my colleague had received a better religious education, one that included awareness of other points of view, along with help to think critically about them, as well as understand the criticisms of his own faith and the defenses of those criticisms, he would have been better prepared and, I dare say, might still be Catholic. That's not to say that no one who well understands the Catholic faith would turn to atheism; however, I am saying that most people who turn away from the faith do so based largely on misconceptions or just some bad experience/ill will towards someone they perceive to be an exemplar of those who follow the faith.
We can only do so much about the latter--try to be good exemplars ourselves; however, we can and should minimize people leaving the faith due simply to being poorly prepared or misinformed. This doesn't mean we treat all viewpoints as equally valid, nor that we don't teach our children the faith, nor that we expose them unnecessarily before they are ready, but sheltering only goes so far.
At the end of the day, our children are their own selves. They will be responsible for the free choices that they make, and just like we work to prepare them academically, socially, etc., we need to prepare them philosophically and theologically. We can't do this by pretending that other viewpoints don't exist or by shying away from hard questions and providing slippery easy answers that gloss over difficulties. They will face these at some point, and if we don't help prepare them, we are at the very least in part responsible.