K.B.
Oh boy can I relate to you on this one D.. My daughter just turned 12 and is going through the same issues. She's dealing with girls who can be just so mean its ridiculous. My daughter did have a few friends but recently they started shunning her and being downright bullying. I was really distraught about this and my daughter was so depressed she wouldn't even go to school. I got her into counseling immediately even though my budget couldn't really handle it. I felt like it was important enough to sacrifice some other things in order to get her some support. The clique thing in school is just ridiculous and its only going to get worse. I felt like there was nothing I could do to change that but I could do things outside of school to make sure my daughter was being fulfilled in other areas. I got her involved in the Youth Volunteer Corps and she's really liking that. I've also beefed up classes in theater, art and dancing which are really her big interests. Of course they have extracurricular sports activities at schools but not theater and art...figures.
My advice is to really take this time to reinforce to your son that he is loved and valued beyond belief and that people just have different interests and that doesn't make them better or worse than anyone else. Everyone is unique and lovable in their own way. It would have been so much easier for my daughter to give in and go play sports so she could have friends but she didn't want "false friends" and to do things she didn't want to do just so she could fit in. I was really proud of her for that but realize it can be a harder road. Find out what your son is interested in and get him involved in that. Also, if there is a church youth group you could get him involved in, it may help him to meet other friends that aren't at his school. I am not much of a churchy person myself but have considered it for this reason and that the church teachings (my interest is Unity church) would also help her self esteem and to feel better.
I've also involved the school counselor. My daughter wasn't really very happy about that but she felt that she was really helpful after she went to see her a few times. I let the teacher know what was going on as well and she has been monumentally helpful in observing the "mean girl" bullying and placing my daughter in work groups with kids who may be more suited for her. Don't be afraid to talk to the teachers. You may be surprised how helpful they can be.
Good luck to you and your son! I know how painful it can be but if you're proactive, you can divert him into fun activities that take up his time and feed his self esteem that aren't sports related. Volunteering is also a really good way to make them feel good about themselves by helping others. http://www.yvckc.org/