Frustrated

I was almost at my wits end today. I worked with three of my sped kids today that all have learning disabilities and gave them a SUPER simple assignment to do back at their desk. We were filling in a graphic organizer and all they had to do what write 9 words down. The two that finished, it makes absolutely no sense whatsoever. They didn't even write complete words down. And the third, is also ADHD and had an HOUR to do this assignment and couldn't stay in his seat long enough to even write one word down. This child's home life is SO JACKED, which is a HUGE reason he is the way he is, but it's so darn hard to get this kid to do anything. And I feel like he needs to learn that school is a time to learn and be serious and he needs to work on staying in his seat for a short period of time at least and doing work. I have NO hard evidence of any work that this kid has done so I have no proof of any grades for my gradebook. He's pretty bright, but he just won't do the work. I feel kind of bad because I made the whole class wait to go to recess until he was finished with his work and of course he whizzed right through it. But I hate doing stuff like that because I know he has a disability. So where do you draw the line? I can't keep making excuses for him because that's not going to help him in the long run. He needs to learn some sort of discipline and no other teacher he's had so far could handle him so they just threw him on the computer and let him play games all day. He is OBSESSED with the computer and he'll sit there forever. It's an easy way out but I don't wanna be one of those teachers. So I sat down with my principal and AP today and got some suggestions. I'm hoping that they'll help. We'll see though. I love the kid to death and I feel so bad for him but it's so hard to figure out how to help him when you don't fully understand what's going on in that little brain of his! HELP!