But that is probably not a very popular belief. There are more severe cases to be sure but almost every guy has some symptoms.
Poor performance in school can just be boredom. And most schools aren't really designed to help kids excel or for rambunctious boys.
I'd just keep loving him and working with him at home and see if he can develop some coping techniques and work on some of the negative behaviors. I'd also look at giving him more play time and less screen time.