L.,
First question I always ask is 'Are you sure your child is ADHD and not suffering from an Impulsivity Disorder.' Both of my sons were diagnosed as ADHD, as well as one of my nephews. They were all diagnosed back in early elementary school, through testing conducted by the school department. My nephew (now 23) and my middle son (17) have grown out of ADHD and no longer require medication & counseling. My eldest, however, has developed something else - as it seems he hasn't grown out of it yet (he's 19).
Suspecting my daughter of either ADHD or an Impulsivity Disorder, I had my daughter tested by the school department as well. It turned out that my daughter had neither - she's just bored and advanced for her grade (the school department retained her a year because her birthday is Sept 23 & the school department's cut-off date is Sept 1). It's a really stupid thing I'm still dealing w/on the school department.
Anyway, what I learned w/my boys & my nephew was that ADHD children learn differently from other children. Working w/the teachers, we found something that worked for the boys. Picture a circle - you start w/one subject (e.g. Math) and in about a 1/2 hour, you'd go to the next subject (e.g. writing), change to another subject in a 1/2 hour, and keep going until you're back to what you started w/ (e.g. Math). Art was also a fantastic tool I used at home w/my boys. Their creativity flowed so amazingly AND they kept on task. Structure is definitely key, in my experience, w/the ADHD child.
With this in mind, I would say to meet w/his current (and future teachers) to work on a plan that will help your son academically. As for the friends, I really feel for you & your son. Friends are important. Its up to you, but you might want to consider some counseling for him - and maybe you. There are a lot of counselors out there that can help both the child and the parent(s) w/coping skills to lead a full life.