K.,
You say your son is ADHD. Has he been diagnosed by a child psychiatrist? If not, don't just take the school's word for it because he may not be. Some children learn differently and public school is not a one-size-fits-all education; there is no such thing. Your son may be a kinesthetic learner which means he may learn by being "hands-on" rather than auditory or visual--like all classrooms teach through lectures and sometimes notes written on the board or reading a book. If your son scored above average on his tests, it's likely that his cognitive abilities are beyond what the school is teaching at his grade level.
Read a book called "Dreamers, Discoverers & Dynamos: How to Help the Child Who is Bright, Bored and Having Problems in School" by Lucy Jo Palladino. Look it up on Amazon. The paperback is ten bucks. Before you buy it, also look up the book "The Edison Trait" by the same author--it's the hardback version of the same book. Now scroll down on that Amazon page and read the reviews. There is one long review about half way down that lists the principles/traits of children who have this. Read it and see if you see your son's behaviors listed. This book helped me understand my son (and myself).
Also, go to the Google screen and type in: The 7 Learning Styles, Stacy Mantle. You will come up with hits for an article that will give you an overview of the different learning styles that will help you with your son. She uses the word "bodily" for the kinesthetic learning style, but it means the same thing. Also Google the words "kinesthetic learner" and you will find a ton of information about it. This type of learner is often mistakenly thought to have ADHD.
I know all of this because I fought with the school system from the time my son was in 2nd grade until I finally took him out of 6th grade (at the beginning of the year) and homeschooled him through junior high. I filed an R-4 with the Department of Education and started homeschooling with a traditional textbook style method, but by the end of the three years, we were unschooling, with the exception of me keeping up his math by using Aleks.com, an online math program. There are many options for homeschooling depending on how far you want to get into it--by choosing and teaching your own curriculum to using an ISP through the local school to teach the same classroom material at home.
If you decide to take the plunge, assuming you are in California, I recommend you contact HSC (Homeschoolers of California) it is an amazing organization. Check out their website. They have a conference every year where parents go to fellowship with each other, keep updated on teaching methods, legislation, homeschool success stories, etc. BTW, the book Eragon was written by a homeschooled boy. =) Anyway, the conference is a great place for the kids to see how many others homeschool. There are activities and roundtable meetings for them to do with their peers while you go to other functions. The support system there is incredible. Also, like another mamasource mom said, check your local area for homeschool meet-up groups. HSC has outreach people who can help you find a group in your area. There is a website: www.meetup.com that you can check, too.
The one thing I will encourage you to do, more than anything else, no matter what anyone says (family, school admin, etc.)--trust your instinct to know what your son needs. I waited too many years and fought too many battles trying to keep my son part of the "mainstream." In those three years that I homeschooled, he turned into a different child: his self-esteem went up exponentially, he learned better study skills, he found his love of learning again, and he became so confident in himself that he decided he wanted to try high school. He graduates this June and has completely shunned peer pressure for drugs, alcohol, smoking; he has almost straight A's (one B); he plays sports, has a ton of friends, is considered very mature for his age, is taking college classes to use as electives for high school requirements, and most importantly--he's happy. The child who wouldn't listen in class, ran across the tops of desks, failed tests and classwork, and cried saying, "Everybody hates me. Everybody thinks I'm stupid. I hate myself." That boy is gone.
Good luck. If you have any other questions, feel free to contact me. ###-###-####