Regarding my comments about kids changing their behavior, I was just thinking about my son’s “vanishing mittens.” I remember telling him that if he put on his coat and his mittens weren’t there, he had to stop everything and demand that the noone go anywhere until the mittens were located. Eventually they turned up in this other kids’ backpack. It was partially a matter of self respect, as well as respect for his property, and the efforts of his parents who outfitted him for school. He went to school with the mittens, he should not have to walk home with cold hands. No one should be able to make him do that. If something wierd and unpleasant is happening to you, you should try to figure out the cause and prevent it from recurring. And we should not have to go through the effort and expense of replacing them.
I never recommend physical retaliation for several reasons. Kids who strike are often treated far more harshly than kids who provoke a physical response. It is easy for a kid to get a rep as “That kid who hits.” Also, the experienced bullies are conscious of hiding their aggressive actions, whereas you child’s unsophisticated response is far more likely to be noticed and punished. Like in a footbal game where the flag is always thrown following the second hit. Finally (and probably most importantly) as appealing as it might be at times, you don’t want your kid thinking he can solve all his problems with his fists.