Oh, and there's an argument to meet your second point. Most Protestant denominations have a set of core values they all espouse. There are a second set of almost-core values, of which there are three or four broad sets. After that it breaks down considerably, but it would be possible to group them together to form some broadly similar ideas, and teach those. Then you either leave out the parts where they differ, or you teach the differences side by side and let the kids choose. There's also the argument that most of Christianity believes almost the same things when you get down to brass tacks, and the public education could focus on those and leave out the nitty-gritty. You'd still get the prayer in schools, and the "what would Jesus do?" type emphasis. That's basically how the Catholic schools here handle it. (Yes, I've seen them from the inside - I taught in one as an assistant for a while in university.)