My DS is in Yr 12 now. Our experience of his GCSEs was so bloody frustrating. He is a happy, sociable, lovely, bright boy...who is also lazy and didn't see the point/need to revise.
At our school they don't give homework, they only have to do anything at home if they don't finish the class work. This seemed to make DS think there was no need to revise, and as nothing had been set I don't think he quite knew how/what to revise.
DS was of the opinion of if 4/5s are what you need to get into college, why bust a nut getting higher grades. I could see the teenage mentally of that, though found it really frustrating that he was capable of getting higher grades so why not try to get them.
I would say honestly he did no more that a couple of hours revision for his GCSEs, I mean in total...yes we could have taken phone/xbox away and made him stay in his room but that still wouldn't have meant he actually did any meaningful revision, just would have caused a whole lot of tension and conflict in the house. DH and I decided we needed to let him do it his way and if he failed then it was a life lesson and he would have to deal with the consequences.
I was quite terrified on GCSE results day, he ended up with 4s and one 5. He was disappointed (as were we, but we weren't surprised). I think he really thought he'd sail through and get 6/7s for everything, his predicted grades were 5-7s, I guess they predicted those thinking he'd actually do some revision.
It actually hasn't changed anything for him, he's at college, loving what he's doing. Do I think it's changed his mind and he would work harder next time...I aren't sure. He was disappointed but it almost might have been better if he had failed and needed to resit, it would have shown him that he should have worked harder and prevented a wasted year resitting.
So sorry OP, I don't think I've helped here at all just giving our experience. I think if your DS is doing an hour a day of meaningful revision at school, I'd be ok with that. It is only November,