Yes 7 year old ASD DS with moderate learning difficulty. Takes 2 hours to write 2 sentences.
I keep losing my posts but in summary:
Try to incorporate some learning through movement.
Maths - and BBC Bitesize Daily also has movement with Maths in their sessions.
Now press play have 4 free audio topic movement/drama audio recordings on their site (best with wireless headphones but could also be played out loud). nowpressplay.co.uk/at-home-free/
Ladybird audio adventures are also good and could involve imaginative play/drama/movement.
Literacy - Kung Fu punctuation when putting punctuation into work.
If you want him to sit and concentrate for longer you could try doing some physical movement just prior to the time that this will be required to help him wiggle it out of his system before hand.
Wobble cushions work sometimes to help with sitting, fidget toys and allow a degree of noise making if he still works whilst doing the noises.
Give regular breaks, sand timers are great for this.
Remember with 1:1 support at home what would normally take a whole hour in class to learn can take 15-20 minutes.
Use a mini whiteboard and pen for some tasks (you can photograph the board as evidence of work), kids love using these.
Use physical resources like Numicon to do maths work.
Play learning games like the ones that Orchard games do.
Do kitchen science, make ramps with cars to learn about physics etc..
Learn around his special interests if he has any, you can learn literacy, maths, art etc... through special projects that get his attention (e.g. make a information poster about tigers gives you reading and writing, 5 X table using tiger claws on each paw, paint a tiger).