It is not developmentally normal for a 6 year old to maintain "control" and sit all the time. School want a 6 year old to act like a 9 or 10 year old. At this age, especially boys, children move around a lot, need to have an outlet for a release of energy , and be allowed to "just be a kid". I can bet there is nothing wrong with your child, just too high of expectations for a 6 year old child, and normal development.
It really does sound like your child may be bored in class and needs more advanced work. This is something you will not find in the school system, for they teach to pass the test so they gain more money for that school...and concentrate on the children that struggle ion order to maintain the "grade" to attain more money. Smart children tend to fall into the cracks, and if they see your child is excelling academically, they tend to not pay as much attention to them, so he may be seeking attention as well--all normal for this age.
To teach self control, he needs to see it, and imitate what he sees. If all he gets is negative reactions, he will start to crave that since that is better than no attention at all. Again, this may be why the misbehavior is happening in class--attention!
The punishments are not working--time to do something else...Do more positive things with him...get down on his level and just play with him...whatever he is interested in--let him make his own mistakes and learn from them, as well..This IS the age to do this.
home schooling is another option that works very well for many families, and works so well. Florida is a very home school friendly state, and there are so many great things for them to do in order to learn, as well as some great groups for social activities, academic, and support. 6 years old is not the time to have a child sitting for so long...
You may want to also have the teacher give him breaks to perhaps run once or twice around the room, do some jumping jacks, run in pace, or other activity that may help him focus on behavior a bit more. But in all honesty, it sounds like he is either bored, or is craving attention, and he will get it any way he can...even if that means in a negative manner.
Plus, you mentioned that all he is getting at home is negative attention, and nothing positive--this may be teaching him that this is all right, and that negative attention is just a good a positive attention. Change your attitude and perspective, and i bet his will change as well...:)
And you are not a failure!! You are a parent, and we all make mistakes, learn from them and go on...:) It's part of being not only a parent, but being human. Just chalk it up to a learning opportunity for you.