Thank you for your responses.
I have a concern that this policy is inappropriate for primary school children, unless they are in a particularly vulnerable group or area. My DGC are going to be subject to this policy and the school intends to "talk to all the children about extremism" according to the letter that parents have received. These could be 4 year olds in reception in a rural primary school.
I have looked at the websites of several schools and their approach is to generally foster the children's self-respect, to foster multiculturalism and to make sure that proper web filters are in place, rather than talk about it explicitly.
I can see where the government is coming from with this policy, especially in view of Iam's post above, but in the context of a small rural primary where there are no ethnic minorities (apart from a few E Europeans) it does seem inappropriate to be introducing the children to such dark ideas when they are so small.
The problem is compounded by the fact that the school in question has made some dubious (well - frankly crass) judgements when talking with the children about current affairs and this has caused some distress for some of the children, particularly the younger ones.