I think it's a pretty rare third grade boy who's self-motivated to do work. Ask them to play video games, ride their bike off ramps, tease their little sister or whatever else is active, challenging and competitive and you're probably good to go.
Is there a local homeschool co-op so you could have PE together?
Does your son care that he's sitting there all day? Is he playing games in another window? Or is he designing the best race car, video game, story or what have you in his head while you're getting more frustrated? Is he just bored with the material? He might be capable of much more complicated ideas in literature and history and just not have his written expression skills be up to returning that information to you.
Does he think that if he spends a certain amount of time doing school, that there will be less time spent on it later? I can see a kid thinking "Well, I spent all those hours being stuck on school so after 7 hrs/day * 180 school days = done! but I've spent 10 hrs/day so I'll be done in no time at all!"
I used K12 as an independent and liked it for the most part but I do have to say that it doesn't seem to be working well for your son. Is he the sort of kid who can analyze what's going on with him and tell you what's working and what's not?
I'm not sure I helped at all,
NHWX
Self-motivated might be the wrong word. I want to be able to give him a sheet and have him read the directions and do what it says. He will not even read the directions or he says he does and he doesn't understand which I know is usually not true.
He does not care that he is sitting there all day. I know he's not playing games on the computer. He can't spell, the only way he can get on a website is if his sister types it in for him, and she's not home during the day. He just sits there breaking pencils.\ Not sure why, but we go thru pencils like they are water. He gets shocked every single day when 3:30 rolls around and I tell him it's time to pick his sister up. Then he gets upset because he's not done and he can't play with her. He also knows that means the other kids are getting out of school and he can't play with them either. He knows that he still has the same amount of work tomorrow, plus whatever he didn't get done today.
I would say the cirriculum isn't working, except that we used it all last year and he enjoyed it and we were able to finish in 2-3 hours each day. He loves the history and science. We are in the middle of 3rd grade, so it's not even the 2nd-3rd grade jump that is the issue. We dealt with that in April and got thru it w/o any tears on my end. I really feel that he just doesn't think he has to do it for whatever reason. I have him doing Saxon Math 4/5 right now and even that is easy for him. I'm hoping that it's just the "review" and things will pick up soon. I gave him the assessment and that is where he tested.
I am pretty sure that if I could get him more confident in his writing he could sail thru the curriculum at a faster clip. This is one of the reasons I let him do most of the answers orally, or dictate them to me. My original plan was to accelerate him 1 year, but until his writing improves I cant move him any faster. I have no idea how to get him to be a more confident writer and at times I feel that I am hindering his writing development by letting do so much orally. Today when we were doing "real" school, I made him write all the answers out and he did it, w/o much complaint. Now it was barely legible and had no punctuation but he did it and I didnt make him correct that. History he did in no time. By the time he got to his homework (literature) he took much longer (2.5 hours). His LA assessment was the same thing, barely legible and no punctuation/capitalization. Because it was a test and it was Language I did make him go back and correct those things. It wasn't until dinner was ready and we told him he could eat after his work was done that he decided to do it. When I checked on him about an hour in he just looked at me and said "I'm being lazy."