Hi,
I'm homeschooling here so "I feel your pain." I have found that with my son..there usually is a "reason" for the the behavior that you are talking about. Perhaps he believes that the problems are too difficult or that he is simply overwelmed with the number of pages or uncertain about a negative outcome with any errors. I often have to make loving accommodations for my son..either sit with him and work through the problems or cut it into smaller chunks or simply make a game out of it. He works a problem, I work a problem, etc. It is more time consuming but the right outcome... work completed, happy child, happy mommy and family off to the swimming pool.. it is worth it. Maybe consider it a happy one on one time with him. You might be surprised how much you and he enjoy it. It is an opportunity to be the teacher you want him to have in school. Have fun this summer!
I am guessing that your son feels overwhelmed, looking at 8 whole pages of work to do. For a kid with ADHD, organizing that work or calculating the time it will take is overwhelming. Keeping the focus to get the work done is VERY difficult. It probably looked impossible to him and so he took "the easy way out." When my daughter was in 5th grade she used to lose focus between the multiple steps of a single math problem and I had to stay with her and keep directing her and coaxing her onto the next step. It doesn't do any good to compare your son to his younger brother since I'm guessing the younger brother doesn't have ADHD.I have to agree with 'inspired,' I wonder why this is so important to you that he does it.
I also have 2 boys, and with many things the 6yo is much more responsible than the 8yo. I remember my younger brother being more responsible than I was too. It wasn't a good feeling. Maybe your older son is feeling badly about his younger brother showing him up, and it's making him rebel against doing the work even more. Just a guess, obviously I don't know him.
good luck.
8 pages a day! If I was a kid with adhd who thought he'd finally gotten a break from school, I'd put my head down on the desk and cry, too! Eight pages a day are way too many. I get wanting to keep them up to speed over the summer, but 8 pages a day are just too overwhelming. And...worksheets are an intelligence-killing, imagination-draining waste of time. Just busy work. There are LOTS of other things that they could do to keep their grey cells stimulated.
As far as your younger son cooperating and your adhder not cooperating, we as adhd parents have to know that comparing our children and setting them up to be in competition, however unintentional, is detrimental to siblings and their relationship with each other. You have a son who needs to be seen as a valid, valuable person on his own, not in comparison to his little brother. I would be livid if my son's teacher at school compared my kids! Let them have fun together instead of competing at home.