Hi,
I think you maybe worrying about the wrong thing and trying to fix a problem with the wrong solution.
You have a 12 yr old boy, going thru an emotionally trying time, who finds it hard to sit alone at a computer all day long for tedious virtual classes. There is a reason we have long taught children by sending them to a classroom. Many people need that type of setting to remain engaged in any kind of difficult work. Your son is physically and emotionally disconnected from the learning process by the fact that it's all online right now. I have friends with kids who have been plunged into severe depression by this experience.
I suggest asking youself what life skills you think it's important for him to learn right now. Typing skills will help him alot. Keeping up with math if possible would be good. Doing a bit of writing and reading will keep those skills up. Does he know how to do laundry? Cook? How's he doing with personal hygiene habits? (a lot of boys could use some help with that) What is something he loves that you can nurture as a way to nuture his self esteem? Elaborate Legos? Remote control planes? Ask him what he would like to learn over this year. Guitar? This can be a time you use to expand his world view. Go on youtube and find a documentary for him to watch. Nat.Geo 101 and Absolute History are both great sources. Watch it together or assign one a day during the week and call him at night to discuss what he saw.
Then spend a couple of hours every sat and sunday working one on one with him in these areas. You can use school materials for some things or to take the pressure off of him and you, pull him out of public school for the rest of the year and home school him with your own curriculum of life skills. This can become a time he gets attention from you and you may find your relationship with him deepens. Just keep it low pressure and take the long view on this.
Raising a boy takes years and years. If he misses out on a 7th grade science class it's no big deal. If he's feeling lost, alone, incapable, and depressed then that is a big deal.
When developing my goals for my 11 y/o twins for this year I also talked with them about what they wanted to learn. They requested learning music. So, they take a Facetime based 30min music lesson once a week and we include short daily practice session as part of school. My son wanted to learn to ride his dirt bike better so my husband has made that a priority when possible. My daughter wants to learn about animals and being a vet so she watches lots of documentaries on animals and writes reports on them or tells me about them in great detail. My son has also been using an online fight simulator to learn to fly and he's doing so well we're going to try to get him a better set up.
My goals for my kids this year are:
1. typing skills- typing.com
2. keeping up math (we use Math You See)
3. Gradually improving writing. I let them pick a documentary to watch on any subject that interests them and they write either a paragraph or 5 paragraph report. They use a computer so as to work with formating and the like.
4. Developing personal hygiene habits without mom nagging
6. life skills- cooking, baking, cleaning,
7. dog training- we set up a simplle agility course for our dog and the kids are learning to teach the dog. I can't tell you how many social, communication, attention, and empathy skills this requires!
8. learning some more spanish- duolingo.com
9. World history- found lots of videos on youtube
10. Cultural divisrsity - again youtube documentaries
11. primary goal- happy children who still love to learn and are ready to jump back into school next year. This goal requires flexibility. Some days are good learning days and some days are more about meeting emotional needs of kids stuck at home and missing friends.
I never thought I'd homeschool my kids and I'm eager for them to return to in person school next year. However, I've found that for my kids, homeschooling rather than online schooling took the pressure off both my kids and me as well. We school when it is convient for me and when the kids are in the right spot emotionally. Some days I push the hard stuff (math and long reports) and other days we focus on funner stuff.
Sorry this is so long but I was trying to paint a picture of a completely different way of looking at your son's situation and a whole new idea on how to approach it. I hope it's helpful. Parenthood is so supremely challenging and if you're going thru divorce and covid it's gotta be quite a load. But life and growing up is a long haul game. Maybe let go of the traditional fears and pressures of school and re invent it into some thing that gets you and your son thru the year with heart, soul, spirit, and a love of learning intact.
Good luck!