Ohiodad, you say spanking worked for you. It may well have. Your daughter is also well-behaved and you are in charge of her discipline. But please believe me, even if society fully endorsed your methods (and I am not saying there is anything wrong with them at all) they may be a bad fit for this boy, especially under the circumstances (conflicting messages).
I have spanked my kids. I actually stopped spanking the older three very early, because I was given other strategies. Those strategies did not work on difficult child 3 (the youngest) so I went back to spanking. Then I realised that in his case, spanking him was actually teaching him to use violence on others to get what he wanted. Again, this was not something that happened with easy child. Looking back, I do see it was beginning to happen with her younger sister until we stopped because we didn't need it.
When we on this site warn you against spanking, we're not doing it to tell you to go soft. Far from it. I have heard kids say, "I just wish my parent would spank me and get it over with. But no, I have to get a lecture and get grounded!"
When it comes to you (or your wife) spanking this boy, you have a number of obstacles to this method:
1) His father, who in his disapproval is undermining this as a viable discipline method.
2) The attitude of onlookers whose finger is so often on the speed-dial button to CPS.
3) His age - at 12, you shouldn't need to spank any more.
4) It's not working anyway.
Now, why is it not working? Why are there problems?
That is where you need to ensure there is no underlying disorder that could explain some or all of the problem you're having. It could simply be a case of confusion plus inconsistent parenting plus a lot of anger that his parents split up and you are on the scene. Or it could be that there is a mental disorder of some kind, either inherited or imposed by the lousy hand the kid got dealt. But if you haven't had this checked out, you could be putting the cart before the horse in trying to discipline a kid who has so many other issues that your discipline just can't work. It can be like punishing the blind kid for failing to copy accurately form the blackboard; if the teacher doesn't realise the kid is blind, they will make assumptions about the kid's ability that are not workable. But once the teacher knows that the child is blind, other supports can be put in place so the student is given an alternative route to getting the education he needs.
Changing direction on discipline is not a sign of weakness; it is actually strength. Weakness (and insanity) is doing the same thing over and over, and expecting a different result.
I would bet money on there being an underlying disorder; if your discipline is working so well on your daughter but not on this boy, that to me is another warning sign that there is something else wrong that needs to be identified, before you can make effective progress.
All your work with this boy, all the school supports - he is throwing it back in your face because he is needing constantly to have your love for him affirmed. Again, it's a bad habit emotionally, he is learning to use passive-aggressive arguments to get the wrong kind of attention. it could well be learned behaviour, probably from his father.
Do not take his remarks personally. Just don't react. The day will come, maybe it could take another ten years, when he will look back and really value what you have done for him. And your reasons for doing this are not to get pats on the back; merely to know you are doing a good job, to know this in your own heart.
I had to really drive difficult child 1 hard in his schooling. I'd pulled him out of mainstream, he was 17 and failing because they were not able to support his needs. So we enrolled him in correspondence and I had to really push him hard at times. Sometimes I felt he really resented me and my efforts. He grumbled, he complained, he was really difficult at times. But we got him through to graduation. And my reward - a couple of years later I overheard him telling his friend, "You should have had a mother like mine. Without her, I wouldn't have graduated. I hated it at the time but I am now so grateful to her."
He's 27 now, life is still a struggle and he is determined to do as much for himself as he can, but he is who he is now, because of the efforts we put in when we did.
So whatever happens, whatever decisions you make, your efforts so far with this boy are making more of an impact than you realise.
Marg