My Son Is 7 Years Old And I Believe He

My son is 7 years old and I believe he is suffering from some sort of mental issues. I don't know if he is going through something right now or not. He has severe fits of rage no matter where we are or who is he with. He can not sit still or stay focused on one thing for very long, unless it's like a video game, or something, then it's like he is transfixed on it. He can not calm down when it's time to be calm. If he has to wait his turn for something he can not do it without a fight, so to speak. Everything is an argument if it is not what he is interested in doing. He does wonderful in school and gets amazing grades. However, he is a totally different child at home, in the store, friends or family's house, the babysitter. Everyone, keeps saying he has adhd, but is that possible with him doing so well in school? I don't know if it's the structure of school activities or what... but I don't know what to do or what is going on? He has always been on the go, but these behaviors have just got worse over time.