after having a good few working herders, as a lot of you have stated, its very very hard to get the dog to stop after its done it once.
in my opinion, as IanB says a clout acros the lugoles makes your statement rather clear, and if it continues, dont take the dogs near fields with life stock.
farmers are having hard enough time keeping stock up as it is with out boys letting their dog get away with things like this.
TD17