I'm not sure how to advise you...I wish I had more information because the possibilities are virtually endless.
I would definitely suggest that your son's behavior is a bid for attention and caution you against letting it turn in to a cycle that teaches him that it is a lot easier to get attention for negative rather than positive behavior...I'm dealing with this mistake in a seven year old now and it is not fun!
I'm also concerned that your son's teacher(s) is unable to redirect his attention and seems to be focused on coming up with increasingly obvious forms of negative reinforcement...if this is happening in pre-school, I imagine it would be deeply ingrained by first grade...thankfully, my son's pre-k and kinder teachers saw his behavior as a bid for attention and gave him more positive attention when he began acting out...I can't imagine how badly he would be behaving now (second grade) if I (and his teachers) had allowed the negative reinforcement cycle to escalate the way we did this year before we recognized what was happening!
...one thing you may want to consider stems from what you said about circle time and the way he plays...my son was EXACTLY the same way at that age...and even now he has a hard time containing his excitement or sitting still...and while any number of people have tried to suggest ADHD as his problem, I (and fortunately every teacher he has ever had) know that he is really just an unusually gifted child in ways that make it difficult for him to follow rules or engage in activities that he deems "pointless". His second grade teacher recently described him as "seven going on thirty".
I'd urge you to consider the possibility that your son is similarly gifted and that he may have just figured out that behaving badly is an effective way to get the attention he wants!...and if this is the case, the best solution is NOT to give it to him by providing a list of rules he can break to ensure you and his teacher will focus your entire attention on him! Instead, find ways to offer him positive reinforcement and make the negative reinforcement truly negative by denying him the attention he seeks.
For example, my son bit another child in pre-k...and instead of getting in his face and lecturing him about his behavior or sending him to the office, the teacher made him sit in a chair beside her while she lavished all her attention on the child he bit! Using similar methods for other incidents, my son quickly learned that hurting another child doesn't get him any attention...it focuses all the attention on the other child and that behavior stopped completely.
I'm not suggesting you do away with rules and negative consequences...just make sure that your son is getting a LOT more positive reinforcement than nagative...at school and at home. It is far too easy for us all to ignore all the wonderful things our kids do and focus too much of our attention on their mistakes...and doing so teaches them that bad behavior is the best way to get the attention they crave! Ask yourself this...since solving the letters problem, how much praise have you and his teacher given him for writing his letters?...how much affirmation, praise, and other positive attention does he get when he does follow the rules, when he does sit still in circle, when he does stop playing when he's told to do so? I think it is far to easy for us to come to expect certain behaviors from our children and we stop rewarding them for those behaviors...instead, we notice the exceptions to our expectations and all too often end up teaching our children that negative attention is better than no attention at all!
Please know I'm not criticizing your parenting in ANY way...I think this is something we all do. It dawned on me (and his teacher) this week that my son hasn't received a lot of positive attention for the past few weeks...that we both have been so focused on making him follow the rules that the bulk of the attention he gets has been negative (e.g., loss of privileges, lectures) and his behavior has continued to get worse. During our teacher conference yesterday, we (the teacher and I) resolved to concentrate on giving him a lot more positive attention for all the things he does right while at least temporarily ignoring some of his negative bids for attention.