I used to have bother with a group of lads at school. All of them thought they were hard within a group. However, when I singled one out and kicked him full pelt in the 'nads - it turned out he wasn't so hard after all.
I did take a beating from him and his mates after this incident. To sort this out, I simply waited until the same lad was on his own again, gave him another beating, and warned him that I would keep on targeting him if he had to get his mates involved. It ended there and everyone got on with their lives.
I'm not suggesting you should take the approach I did, but Adrian's right, you have to find your own way of dealing with bullies and sometimes that does mean standing up to them one way or another.
