My Y1 learned to write when we took several extra weeks off school to travel in the US. He kept a journal, which consisted of taking photos of anything he wanted and writing about them (a few misspelled words).
I would buy your son a lovely, hard covered, blank, unlined, journal and get him to write/ draw/ stick in things he finds interesting.
I have 3 older kids who are all good writers, and I NEVER corrected spelling or even told them how to spell anything. I think they learn by sounding words out for themselves, and if you correct them it knocks their confidence. If they asked whether something was spelled right and insisted on an answer, I would say something along the lines of: "that's a pretty good way to spell that word.....I think most people spell it 'knapsack' because spelling is kind of silly sometimes".
I think schools often take the fun out of learning to write, so I would avoid anything that makes him "reluctant".
For reading, I would find interesting books he loves, and read them aloud to him, no matter how difficult, (if he doesn't like the dreary school offerings). My son was bored by beginner books, but couldn't read anything harder because he couldn't be bothered to try. Then he got fascinated by Tintin, which I refused to read aloud, so he learned on that, even though it was HARD. My daughter was obsessed with Harry Potter books on tape, and went from reading about cats on mats to reading HP, which she could only do because she knew pages and pages virtually by heart.
Reading this over, I'm thinking maybe this isn't helpful, because it's all about our family, and might sound like I'm bragging about how much fun we had learning together blah blah blah.. I guess what I'm really trying to say is, learning to read and write is so much fun IF you find the right things which actually really interest you and him. Faking it doesn't really work, I don't think; kids can tell when you are trying to "educate" them and they tend to close up and resist.
What does your son love most?