We don't teach quantum mechanics in primary school, or go into the detail necessary to make clear the circumstances in which Newton's laws don't actually hold. But there's no public outcry against the physics teachers for brainwashing our children and filling their heads full of stories which the teachers themselves know to be lies. Why is this? Because by the beginning of the 20th century, the complexity and sophistication of the best available theory of the physical word had reached the point where is was literally incomprehensible to people without extensive specialist training. The curious among the rest of us dabble in popularisations, more or less inaccurate, and the superseded 19th century stories, because they can be grasped without years of postgraduate study, are, correctly, judged appropriate to be taught to our children. Although false, they lead to the right conclusions in most ordinary circumstances. Treating them as true gives the right results, even if not exactly for the right reasons.
As for physics, so for metaphysics, ethics and theology. We don't teach Heidegger or Tillich in the schools, indeed we barely teach metaphysics at all, certainly not by name. To the extent that ethics and theology are taught, it's a highly simplified, traditional kind of teaching, based on very old stories and images. The secondary-school teacher or Sunday-school volunteer hasn't read, and wouldn't understand, much less be able to teach, the complex and sophisticated theories of metaphysics, ethics and theology which have developed since Aquinas and Spinoza. But there is a public outcry about this state of affairs, most recently and stridently by Richard Dawkins in The God Delusion.
Just how similar are the two cases. Clearly there are important differences -- are they sufficient to justify the asymmetry of the responses? The most obvious difference is that the intellectual landscape of physics, and theories of the material world in general, is simpler in two related ways than the corresponding intellectual landscape as regards the immaterial. Firstly, for the last 200 years or so there has been a broad consensus about the methodology of physics (a combination of mathematics and "the scientific method"), and secondly that although at the frontiers of our knowledge of physics there is uncertainty and debate between conflicting and incompatible positions, overall there is a legitimate sense of progress: our theories today are refinements of and more true than, say, those of Dalton, Newton and Lavoisier, and they cover more ground. There is no corresponding consensus in theology or metaphysics, and not much sense of progress either. Although 'modern' metaphysics and theology are much older than 'modern' physics, dating back as they do at least to Aquinas in the 13th century for Europe alone, there is a large range of debate and disagreement across the whole spectrum of enquiry, even within the Western, Christian tradition, to say nothing of the even greater diversity across the traditions. And if there is any legitimate claim of progress being made, it is not at all the kind we see for physics, where a consolidation of consensus about a wide range of relatively simple questions serves as a stable foundation for further enquiry, but rather some tentative suggestion that a number of different traditions, reaching upwards from different foundations, may be showing signs of convergence at the summit towards which they are headed.
Where we can see three distinct phases in the evolution of physics, we find only two for metaphysics. For physics we have first the diffuse, qualitative narratives of the Greeks, Egyptians, Chinese, Maya etc, then the consolidation on a concrete, quantitative foundation exemplified by Kepler, Newton and Maxwell, and finally the huge leap in sophistication, abstraction and scope of General Relativity and Quantum Mechanics. But for metaphysics we have only the first and the last: the diffuse, narrative phase at the origins of the major world religions, and the much more sophisticated and abstract metaphysics and theology exemplified by Aquinas and Tillich, Kant and Heidegger.
The key point is that whereas for physics we have the intermediate stage, as exemplified by Newton, which is pretty accurate, reasonably accessible to ordinary understanding and subsumed rather than contradicted by the most sophisticated current thinking, there is no such intermediate stage available for metaphysics or theology. Unable to choose from or teach any of the modern, sophisticated, abstract positions, we are forced all the way back to the too-simple, too-obviously-outdated narratives. It's as if we threw up our hands at the complexities of Quantum Mechanics, but had only Democritus to fall back on.
Like Newtonian physics, Bible-story Christianity has practical value as a basis for beginning to understand our world and learning to behave in it. But unlike Newtonian physics, too much of the argumentation behind it is not just inaccurate in detail, but downright misleading and contradictory. The fact that modern theology and metaphysics can provide fully articulated accounts that don't have these flaws is irrelevant to, for instance, Dawkins, whose ignorance of theology is, after all, matched by that of the great majority of those he is criticising.