I have a solution for your son! My husband and I have ADD and our 7 y/o son has ADHD, so I am extremely familiar with this topic and have struggled a LOT myself with this disease (yes, I am calling it a disease). I was on Vyvanse for a while, but the thought of taking it for the rest of my life was depressing, as well as unhealthy. I researched this topic a LOT and learned that a very high dose of omega 3 fish oil is the solution. I'm talking about EPA and DHA. The more of them, the better. You need to go to your local health food store and buy a very good quality fish oil (I use Nordic Naturals Ultimate Omega) and give your son a TON of it. 2 of my soft gels contain 650 mg of EPA and 450 mg of DHA, however, with my ADD brain I need more than 2. I take 4. Another great brand is Jarrow EPA-DHA balance. You son would probably need 3 soft gels (each soft gels contains a bit more EPA and DHA than Ultimate Omega - I used both brands, depending what's on sale). FYI - you CANNOT overdose on omega 3's, so you can give your son as much as he needs without worrying about a fish oil overdose! Omega 3's are the best "medicine" you can give your son - way better (and so healthy and natural) than a prescription ADHD medication! If he doesn't like to swallow soft gels, you can take a sharp knife and puncture the soft gels and squirt it in orange juice or any other drink and have him suck it down. That is what I do - I squirt them in my smoothies.
Another solution - healthy, nutritious food! Proper nutrition is super important for everyone, of course, but especially for people w/ ADD/ADHD. Your son needs to eat healthy, well-balanced meals! Start his day off w/ a very good breakfast - a healthy whole grain carb, a protein, and a healthy fat - example - a whole grain waffle, bagel, pancakes, etc., with eggs or turkey bacon cooked in extra version olive oil. The e.v.o.o. is the healthy fat. This combination is like food for our brain and helps stablize our mood and helps us focus. FYI - the EPA is a mood stabilizer, and the DHA helps the brain to focus. The combination of both of them, as well as proper nutrition should improve your son's ADD immensely! Try to have him eat a whole grain carb, protein and healthy fat at every meal, if possible (and don't forget his fruits and veggies). Forget the therapist, forget prescription meds. Do what I said and sit back and watch your son's improvement in school (and his mood)! And if you don't notice a big enough improvement - just increase his omega 3's. Best of luck
One more thing - you may want to get him an in-home private tutor to improve his failing grades. That is what I do with my 2nd grader and he loves his tutor and it's helping him a lot!