I think your son has lost his way. It's great that you're looking for others' experiences on MN.
MN never fails to amaze in its inability to walk a mile. Everyone thinks their 'lived experience' is the same as everyone else's.
My eldest was a bit of an issue. In a good school who supported him every step of the Y7-11 way. He was at 15, lazy and unmotivated. It was driving a serious wedge between us to the point where I had to tell him, Feb, pre GCSEs that I would try and stop nagging as it was destroying our relationship.
He duly underperformed in 6/10. Not badly, AABBBBBBCC. Thus onto sixth form with the same attitude.
By half way through Y12 it was evident, the direction of travel. He attended, sure, but the work wasn't being done. So I stepped in and changed that direction.
I was calm, I was 'considered', but I said 'A levels are over, you need an alternative, but that alternative isn't sponging off me. You're PT at Tesco, you'll go FT. You're not 'doing nothing'. It's fine to work FT in Tesco, there is no shame in that. Many, many do. But you're not sitting in your room gaming, at my expense, darling. One day, dad and I won't be here to support you and bail you out.'
Then I found a 2 year, 3 A level equivalent extended diploma BTEC in computing at a local tech. Which he enrolled in. Knowing his A levels weren't happening.
Suddenly, he got it. Aged 17. A few ups and downs, but the beauty of a BTEC is you're constantly handing in work. A couple of exams only.
He's now in his final year at uni doing software engineering.
I hope your son will mature enough to change direction. A levels may not be for him since it's falling apart in Nov of Y13.