Correct me if I'm wrong, but it sounds like most of the problems are school-related, and the problems you have with your DS at home arise because you are 'on his back' about his behaviour and achievement at school... Which is perfectly understandable, but possibly not an approach that will actually work.
I'd be willing to bet that he is one of a largish minority of kids who learn through doing (known as 'kinaesthetic', 'activist' or 'experiential' learners), and who are not well-served by a school system that expects them to sit still and listen. This is to do with how their brains are wired - how they naturally learn - though many children like this do learn to adapt...
Kids like this find sitting still very difficult, and really someone ought to be teaching them maths (say) by getting them to build a wall: count, weigh, measure the bricks, mix the mortar, learn angles for corners, develop engineering skills if they're especially bright, etc... But instead they'll be expected to work from theoretical examples in textbooks that mean nothing to them and don't engage them. And when they can't and don't, they get into trouble...
IMO, schools punish a lot of kids because they simply can't offer them learning opportunities that suit them. If you think back 30-40 years, to times when left-handed children were punished for using their left hands, you'll get the idea... :(
Some stop trying altogether, and some start to behave badly. Bright kids get especially bored, and often engage in low-level disruption because of it. It can also be pretty puzzling for them, because they know they're bright, and yet they find what they're being asked to do difficult, and they don't understand why. What's more, they're often discouraged from doing the practical subjects they would enjoy more, because they're bright (and we have this weird academic/vocational divide in our education system 
), and pushed to do more 'academic' subjects - then criticised when they don't do especially well.... It's frustrating, and some of them get quite angry and alienated, which then leads to further bad behaviour, and can turn into a really negative 'vicious circle'.
If this sounds like your son, then the chances are that's the root of your problem. He can't help how his brain works, and it's not his fault the English education system doesn't meet his needs; and even if he's not consciously aware of the problem, at some level he'll think it's unfair that he gets into trouble.
If he is also getting into trouble from you - his mum and dad - the people who ought to be 'on his side' - then he's likely to be quite angry with you.
Those of us with kids like this can tie ourselves in terrible knots, because we want our DCs to do well, and we feel we ought to back up the school if our kids are being disruptive. But it's not always the best approach... About a year ago, someone here on MN (and sadly, I can't remember who) said something wise about schools: they pointed out that our relationship with a DC's school only goes on for a few years (7 at most); whereas our relationship with our DC goes on and on for ever. It is simply not worth letting problems at school get in the way of your relationship with your child.
Of course, even if we campaigned to change the education system to suit kids like ours, it won't be done in time to help your son... And you probably don't really want to change your son (or not very much! 
) just to suit the system.
You will have realised by now that I don't think the 'sanctions approach' will work. In fact you know it doesn't work, because you've been using it, without success!
Instead, IMO, you need to help him learn techniques to cope with a school system that doesn't suit him...
In my own case, I didn't work out what was going on until my son was already angry and disengaged - under-achieving in his GCSEs and trying to drop out of education... :( But if I had the time again, I'd do this, and I suggest you try it with you son...
- Help him identify his learning style (if he hasn't already) using info like this
- Help him understand that if he's a kinaesthetic/activist learner, that's not something he chooses, it's how his brain is wired.
- Help him understand school activities aren't very well suited to learners like this, so he has to learn to adapt...
- Help him identify ways he can do things and be active without getting into trouble... Twiddling toes inside shoes? Writing more and faster?!
- Help to negotiate with the school about useful coping strategies - will they let him fiddle with a lump of blu-tack while he's listening, for instance? ('Fiddling' has been shown to help concentration and learning for kinaesthetic learners).
- Support him to manage frustration and anger generally. He'll probably experience a lot of it.
- Help him understand he'll probably enjoy practical subjects more than theoretical ones, because of the way they're taught, not because of how clever he is.
- Make sure he's involved in as many sports and practical activities as possible, to sort of 'balance out' the sitting still he has to do.
- Help him understand he'll have to work harder at concentrating, listening, reading and sitting still than many other pupils; being a kinaesthetic learner doesn't 'let him off the hook'! But because he's working harder, he needs breaks and rewards! Agree what these will be! :) Rewards for managing not to get into trouble area good idea, I think. :)
It's got to be worth a try, hasn't it?! 