Your son's teacher may be misinterpreting his high activity level or what seems to be his difficulty paying attention. Instead of ADHD, these might be the behaviors of a child who can't hear a lot of what is going on around him and who is moving around in order to "see" what people are saying. There are many things a teacher should do for a child with a hearing loss. Using an overhead projector to add visual elements to verbal presentations, providing lecture notes or outlines, avoiding moving around the room or turning her back to your son, repeating questions and answers given by other students are all ways she can help. If the impact of the hearing disorder is not clear, a specialist should come in and observe your son's reactions in verbal and non-verbal environments.
About the issue of your son getting things right or wrong depending on the mood he's in? You should be aware that a learning disability could affect kids in different ways at different times. Also, if he has ADHD, he can't tell when his attentional switches are going to be on or off. These are neurologically based problems that are hard to live with because they can intermittently affect learning. If the real reasons for your son's difficulties can be identified, then the teachers can teach in the right way, you can help your son understand the impact of his learning problems, and he can become a better self-advocate.