I used to work as an intervention teacher with the really stuck kids who were excluded from their classes for not working/not behaving/disrupting other kids, but who weren't expelled. A lot of them had SEN and some also had English as an additional language. Take these as suggestions and ideas, they may or may not work for you. For you as the adult, it's about getting them to not stress over work as this can snowball quickly into a huge barrier to learning.
When I have kids who won't work in the classroom (and now, as a home tutor), I break the work into little chunks. 10 minutes of this. A juice break. 15 minutes of that. A wiggle break. 10 minutes of the other. A Zumba break. I try and make the activities fun and if that means not doing what was set/planned, as long as he's learning the same thing I wouldn't have any issue with that (depends if the class teacher expects every piece of work to be done).
Give him some control without actually giving him a choice about doing work. "Do you want to do your art project or your maths next?" could work, or if that leaves him never doing one thing, "these are the tasks we need to do today, let's plan what order to do them in." Then he is taking part in planning his day. This also works with ASD/ADHD kids (I have ADHD and this helps me too).
Let him choose where he works within reason, so he might want to sit on the floor for one task and at the table for another. Just moving around where each task is done can help him engage.
Don't stand over him waiting for him to start (I know, it's hard when you want to know if he's doing the work or not). Give him a piece of work to do, and then walk away, spend a couple of minutes putting stuff away or something.
When he's absolutely not engaging, turn the work into something he likes, e.g. Lego. Maths? Model it by counting Lego blocks. English? Practice spellings by making the words out of Lego. Science? Lego diagrams. If he likes using the computer, let him do some of the work on the computer e.g. in MS Paint or in a Word document. Take what he's interested in and use that to get him learning. You don't even need to tell him he's doing home learning although he'll probably cotton on.
But don't cave and let him do whatever. As soon as you do, he knows he just has to push until you give in. If you think he's mature enough, maybe a talk about careers, what jobs might interest him, and then explain how his schoolwork is relevant. Maybe find out who his idols are and explore what qualifications they got before they got well known. A lot of YouTubers, singers, etc are surprisingly well-educated (not all).