If you are a teacher I'm probably teaching you how to suck eggs ,so I apologise in advance.
Have a clear routine in place.
Do homework in short bursts rather than all at once. Start with the tasks he finds easiest/enjoys the most so he gets a dopamine hit and a sense of achievement.
Ask the school if they can adapt the homework to his needs. So rather than writing a fact file, could he do a PowerPoint or a poster or an image board for example.
Also with homework, adjust his environment and see if it helps and allow him to fidget ,move , spin in a circle ,lay on the floor etc. as long as he does the work.
Offer help(this can be a pain) in a format that suits him. Play around a little bit. If he can't /won't write a story will he record himself telling it? Will he type it either on a laptop or in a text?
Clear reminders(both for time left until x and now and next type things) and instructions .
Give two acceptable choices. I.E. Do you want to do your English homework first or your Art?
End important (I say important as it loses effectiveness if it's constantly used) requests with a thank you rather than please. So "Go and brush your teeth now, thank you."
Reading. Does he hate all reading? Expose him to a range of writing in various forms. Magazines, actual books , or something like a kindle. Fiction, non fiction. Comic books and novels (DD preferred this for a while as she found reading walls of writing incredibly boring). Various genres , with themes that spark an interest(there are minecraft stories for example if he's into that). Don't necessarily aim for his age , they can be lower if they spark interest and enjoyment.
Most importantly ask him what does he think would help him with x,y,z.
If you post some specific issues you need help with I can try and give some targeted advice , as this is all general stuff.