Having been a Teaching Assistant for over twenty years, I am surprised that a school expects him to do 'homework' before he has even STARTED school; many Reception classes don't do homework, other than sharing books with a parent and starting to learn to read.
I am sorry, Mum, but it seems to me the greatest threat to his success in school is going to be YOU. If he doesn't WANT to do these things, then don't try to make him; and DON'T, under any circumstances threaten, bribe, or invoke in any other way, his compliance.
The chances are (and I stand to be corrected here) that you have for some weeks or months been making a 'big deal' out of him starting school, and now he is scared of the unknown and what it might entail, and is not prepared to co-operate.
Has he been to playgroups, pre-school or any other toddler-type setting? If so, how did he react there? In the course of normal, daily play at home, does he EVER use any mark-making resources? Does he play with jigsaw puzzles, construction toys such as Duplo or Lego?
Do you regularly read to him, as that is probably the most essential requirement prior to starting school? Is he OK with changing his clothes, shoes etc (with help), coping with the toilet, feeding himself, sharing and turn-taking with other children? These are the things that are important at this stage, NOT 'tracing over lines'!