I have ADHD, and I benefitted very well from Stratterra for a number of years. It's a non-stimulant ADD/ADHD medication that doesn't cause as much arousal as a stimulant. It also lasts for 24 hours and doesn't have a big comedown like stimulants do. I felt a little tired and cranky after taking it, so, I took it at bedtime so I would sleep through those effects. By morning, I felt calm, focused, and ready to go to school. I also was able to sit still for an entire class period with only occasional bathroom breaks, whereas before, I felt restless and needed frequent breaks. Unfortunately, I had to stop taking it after roughly 8 years because the maximum recommended dose stopped working for me. My doctor gave me a slightly higher dose, thinking it would help, but, I wound up stopping it because the higher dose caused gastritis (inflammation of the stomach), panic attacks, and episodes of sinus tachycardia (very fast heartbeat with a normal rhythm).
You didn't say how long he has been on guanfacine. It does take one to two weeks to build up in the system to be effective - and, of course, the dose may be to low. You might also look into Intuniv. "Intuniv is once a day in AM, longest duration, least sedating, often smoother and is a new brand." However, neither of these "May not help attention as much as stimulants."
You are walking somewhat of a fine line with his multiple disorders. I have read some very good things about the guanfacine/intuniv meds. But, like all meds - it really takes some careful monitoring. I have seen too many posts on the ADHD forum which I am also the CL to have faith that all doctors administer meds correctly. The standard is go low and go slow and them when you start getting over dose effects - back off. You don't necessarily change just because the dose is now to high. Problem is this takes good communication between the doc and parents.
The ODD is a problem, but I wonder how much the school is adding to the problem. I assume he is in 3rd. grade? This is an age where the scholastic demands really began to increase. If the school is expecting him to be a normal kid and follow all the normal proceedures - they are really adding to the problem. His ADHD will start to make school very difficult for him. This leads to frustration, anxiety, and anger. He needs either a 504 or an IEP to help him deal with the daily routine. Does he have one and is the school following it? Also they can't even suspend him, much less put him in juvenile if he has an IEP which lists his condition.
So big question here is what kind of special education treatment is he getting?
In terms of his ODD, here are some links that I think you will find very helpful. http://www.additudemag.com/slideshow/26/slide-1.html?utm_source=eletter&utm_medium=email&utm_campaign=October
http://www.additudemag.com/adhd/article/9868.html?utm_source=eletter&utm_medium=email&utm_campaign=July
The last thing is that any medicine is not a magic bullet. There are a lot of other things that need to be done - by the school and the home. If the only change in his life is a new medication - it will only be part of the answer. Hope this helps please repost if you have any questions.