Years ago my younger brother was getting picked on and bullied on the playground at school. He was in 5th grade and small for his age. On top of everything else he was also a teachers kid, so his behavior was monitored more closely than most. My mother did not cut either of us any slack and our behavior had to be above reproach. One day he had enough and started to take a swing at this bully. A teacher stepped in and sent him to the principal. When he got home, he and my dad sat down and talked about what had happened.
The solution they came up with was this, the next time my brother was getting picked on he was to challenge the bully to a supervised boxing match at the base gym the next Saturday. Dad would arrange for the boys to both have gloves and reserve the boxing ring for a two hour window. Sure enough the kid started to bait my little brother, so my brother laid out the rules for how he would fight the kid. Every day the bully approached him he would remind him that they could not fight at school and they had an arranged time at the gym.
Dad chose the gym, because a lot of kids had basket ball and indoor soccer practice there every weekend. On the appointed Saturday they went in reserved the ring and checked out the boxing gear. All morning Dad taught him how to box properly. They made sure that everyone saw them waiting. My brothers classmates kept checking in to see if the guy had shown up yet. Of course, the bully never showed. My father figured that was what would happen since to get to the base gym the coward would have had to told his parents. However, the next Monday when the bully started to pick on him, my brother had the upper hand and told him he had his chance on Saturday and never showed up. Since lots of kids had seen my brother at the gym the bully lost all credibility and had to back off. My brother never had a problem again with bullying
We were lucky in that my father was in the Air Force and this incident took place at a department of defence school. We had access to the base gym and the proper equipment. The trick to making this work is taking control of the fight and choosing the safer location with suppervision. You also can't bluff you have to show up even is the bully doesn't. Bullies thrive on making their victims feel weak and helpless. Standing up for yourself very publicly is the only way to get them to stop.
Hope this story helps,