It is fortunate that, from looking at the leading figures in the BNP, they aren't very bright. Many have convictions for racist and violent offences which would preclude them ever working with children or vulnerable adults. What's more, they don't seem to be able to keep their nasty views under wraps, so it's easy to identify them and take appropriate action. As I said above, and John Dusford empasises in Emma B's post, schools are well-able to deal with extremists of whatever view.