Lies and fables

A teacher at a school in Exeter has been criticised for a lesson in which year 5 children (10-11 year olds) were asked to write responses to imaginary letters to Santa. (The lesson plan and materials were produced by the Hamilton Trust.) In the process of the lesson it was made very clear that Father Christmas does not exist and that all letters purporting to be from him are in fact generated and delivered by the Royal Mail. (Read the news report here.) Parents were perhaps justified in complaining that it should not be up to the school to decide if and when to tell the truth about Father Christmas to children, although it is not clear to me that the teacher was not right to expect all 10 year olds to have worked it out already. (I suspect that lots of children continue to play along with their parents although they are pretty sure it's all a game for some time before the parents themselves realise. Children are quite capable, I think, of appreciating when playing along is to their advantage and, less venally, when playing along is something they think will please their parents.)
Anyway, I wonder how far this principle ought to be applied? Are all myths and stories, of any sort, out of bounds in this way? Should a school never expressly attempt to enlighten children and stop them believing in unfounded stories? (You can see where this is going...) I would have thought that it was in fact part of a school's job to do precisely that, whether or not the parents concerned have given their consent. You do, after all, send children to school for them to be taught things... There are, no doubt, more and less sensitive ways of disabusing a 10 year old of a false belief, so perhaps the problem here is less that fact of enlightenment than the means. But that the children in Exeter were being educated is surely not in doubt. Teaching children that there is no Father Christmas leaves room for positive discussion about the value of Father Christmas as a story, of course, so this need not be a wholly negative affair. But I don't think schools should collude in lying to children, even if those lies are thought by many to be harmless.