My daughter is ADHD-Combined, and is 9 years old also. She didn't receive her diagnosis until she was 8, so we spent many years getting calls from school about behavior issues. I'll tell you, the best decision I ever made for my daughter was to pull her out of public school. She was starting to get the idea that she was a bad child, that she was stupid (and yet she has an IQ over 150), that she was a bad reader... it was awful. No matter what support we tried to give her from home, she was bombarded with negative messages all day at school, and it was starting to impact her.
So we pulled her out of public school, and now I homeschool her using a Waldorf-inspired curriculum. She learns by doing a lot of hands-on projects. She has recess many times throughout the day. If she starts hyper-focusing on a certain subject, we go with it, and delve into it in as much detail as she wants to. She is happy, and her behavior issues have improved so much! She's learning, and she's excited to be doing so, which (in my mind) is the whole purpose of education. Through the several homeschool groups we belong to, she's able to hang out with friends who share common interests, and they're very accepting of her, even if she is, ahem, "high energy."
I don't know if homeschooling is something you're able to do, or have an interest in? If not, are there any Waldorf or Montessori grade schools near you? In our area there are even a few charter schools that use a Montessori curriculum. They're more project-focused and hands-on than the traditional public school curriculum, and this tends to work well for ADHD kids. So, that's my suggestion. If what you're currently doing for your son isn't working, it may be time to teach him the way he learns best. It doesn't have to be as hard as it is, I promise! Best of luck, and hang in there.