Subjects are based on the nearest approximation to truth we have, growing out of constant peer-scrutiny at the upper end. Nobody is purged from English, say, for believing in the Book of Genesis, but if a child is studying a science subject - or, indeed History beyond a certain level - it is silly to have them do it if they deny its basic assumptions (if you want to call them that) in favour of some unchallengeable belief. That is the whole point: in education, everything is challengeable, but the challenges are meant to come from grown-up, educated people. If you want to start private schools which teach only what you believe your religion to say, fine - though they will have very little in the way of reputation. If you wan't to spend public money on your private cranks, however, you are no better than some dictator enforcing nonsense, surely?