First of all, I would request a conference with both his teacher and his principal. It may be that he hits and is ugly in class because he is bored and needs to be challenged with more complicated work. However, these behaviors may occur independently of his academic placement. His teacher would be in a good position to know that. The reason I would want the principal in on such a conference is that there may be a hard and fast rule in the Tucson school district about grade placement as it relates to age. That is, operating rules of the school may simply not allow any placement incompatible with age regulations. Chances are, that is the situation with which you are faced. To be sure, it sounds as though your son could use some more time in a good kindergarten to acquire some social skills. He will need these throughout his school career, and kindergarten is a great place to get them.
If the school personnel will not allow your son to be moved to a first grade classroom, you are going to need to supplement what he is getting at school with extra stimulation and encouragement at home. Read to him daily. Take him to the library regularly. Make sure he has toys that facilitate problem solving and creativity. And limit his TV watching. It may sound as though that is putting a burden on you and his stepfather, but the kinds of activities I am recommending are as much fun for the parents as for the child.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.