Yep, I can say that after 37 years in education (well and another 8 or so as the CL on the adhd medhelp forum) that kids with a decent amount of intelligence and adhd start to hit the wall at about 4 grade. The math usually does them in (and its going to require many extra hours of tutoring to catch him up).
In my opinion, he has given up. He has gotten tired of hitting his head against the wall. If this continues…anxiety, depression, and self medication will follow.
While some have hinted at it,I will be more blunt. You need to get him on medication. I have worked with kids in the classroom who were unmedicated. They were wonderful kids. We had a great relationship. I would give them 3 days to finish a test….and they just could not concentrate long enough to do even that.
So yes, as adhd momma said, what you are doing (and you have been trying the right things) have not been working. It is time, while you still have the time, to try something else. Because, once middle school starts, life really gets interesting. I, as several of the above have lots of good information on medication. Just ask and we can send it to you.