My comments, this one and the one below, explain why it took me so long to respond and why my first few drafts didn't work. I'm sorry for the bloggy/confessional tone. Things were less sorted out than I thought.

the line between protecting them from nonsense and brainwashing them.

I think that whatever you do, you teach your children a culture; including your attitudes about information, edges of information and independent thinking. This happens on a daily basis, with everything you do, so I don't think it matters so much what you tell them at the object level. In other words, you can tell them what you think about things and trust that they will keep thinking about it on their own terms (and not be brainwashed) if not being brainwashed is something that you value.

Religion wasn't much of an issue until my daughter was about 5 or so. It just didn't come up. My social experience with religion is that most people are religious and some people are not-so, and no one really cares except for the occasional religious aunt that everyone teases for being a fanatic because she gets all worked up at gatherings with the cynicism of the undeclared atheists.

With children in the family, this changes somewhat. I think this is because children are socialized by the whole community, not just the parents. You can strive for independence, but it's kind of difficult to avoid completely (e.g., playground rules) and I think it can be very comforting to have the help. (Especially from other parents that may be more experienced, insightful or patient than you are feeling at the moment.)

All this to explain that my daughter spends a lot of time with her cousins. Since they are being socialized to be good little believers, they try to socialize my daughter with these new rules they are learning. (It is somewhat competitive, to see if my daughter is learning these Very Important Things. My daughter just has to take the status hit of not having known these things, but she is younger so it just one instance of many.)

Regarding these Very Important Things, I can't tell my daughter that they're Not So Very Important, because she will report this back to the cousin and I will have undermined her mother's authority and defaulted on the support network. What I do instead is confirm, 'Yes, it's true. That is important to your cousin and her family.' Since that's not how I usually talk about right and wrong, my daughter is beginning to learn about different tones and language that I use when we're discussing other people's rules. (She's seen it before. I let the kids climb up the slide the wrong way until a parent tells their kid not to, and then I make my kids stop too.)

Things would be much easier again if she was going to a secular school, but we agreed that the advantages of the better teaching, safety and a pro-education culture outweigh the disadvantages of not being secular. So the weekly religion class is a challenge that I suppose will only grow from here on in as they discuss things that are not corroborated at home. I suspect this bothers her, because a couple weeks ago she asked about angels in a tone of voice that sounded like 'why is the teacher talking about angels anyway?"

I see this as a warning sign, because a kid spends lots of time at school and lots of time at home and should feel comfortable in both places. I think undermining the teacher's authority here would be a mistake (something OK when she is 12, but not at 5). It makes me reconsider my decision to put her in this school, but then I think of the alternatives until my resolve returns. I asked her what she has learned about angels (I had no idea what they're telling the kids about angels) and then told her to ask her teacher about some of the questions we had thought of together. With this, I felt pretty good that I had not undermined the teacher (I had communicated that the teacher was worth listening to and learning more from) and had distanced myself from the belief by not knowing the things anyone probably ought to know about angels. I hope I planted a seed that questions should be investigated, and it's OK to ask people what they think in more detail.

I had been feeling pretty good about my progress on avoiding social religious conflict without compromising honesty but then recently I've gotten in over my head with this and I'm feeling somewhat conflicted. I'll post about that in a separate comment.