best and most healthy bet is for you to find him a local private programming school, or find him a local hometown tutor, I am pretty sure you will find someone or something locally.
unless you live in a 1k population small town, but i would just start from there,
alto 13 years is quite young to be enclosed in a 4 wall room, isolated from humanity, looking at a computer screen for hours.and hours a day, cuz that is what will happen.
that age is the most important age of their lives,
I would just try to convince him out of this boring sedentary lifestyle for good, try to convince him to try outdoor activities, socialize, sports, he is too young to waste his adolescent years in a 4 wall room isolated from reality.
anyways that is just my humble opinion, that is what a keep on saying to my sister, since i have a couple of adolescents nephews which are starting to get involved in the damn computer and game virtual world.
I am doing my best to teach the better and healthy lifestyle than the virtual gaming world,
I keep advising them to do something else, mostly to try sports, school activities etc hang out with their friends… at least until the are 21, then they can do whatever they want or trash themselves if they want that., but not earlier than that, cuz most of the time at their age they dont know what they doing they just too young to understand that adolescent is the most important age, this will define them build their personality for the rest of their lives.
dont let them trash their precious lives without them even knowing what they doing at least not until age 21.
and at least to me is very sad to see child to spend and waste his adolescent age enclosed in a 4 wall room in front of a screen.
anyways, sorry for the parenting session, it was not my intention to bore anyone, but I guess if you really are supporting your sons decision then
a local town tutor or comp tech/science schools may be your best bet.
cheers and good luck