I think you are overstating what impulsivity is. The following are the examples of impulsivity symptoms from the very same source you cited above: "Blurts out answers before questions have been completed."
"Has difficulty awaiting turn."
"Interrupts or intrudes on others (butts into conversations or games)."
All of these behaviors are minor and simply need correction, though impulsivity can be expressed in more serious ways like hitting or throwing things. None of them have anything to do with how a child responds to correction. Of course, the child will repeat the impulsive behavior and need correction or redirection consistently. That is the nature of ADHD. That is not defiance, and that is not what prompts a resource officer to be called to remove a child from the classroom.
Ok, I think I see what you're getting at now and I mostly agree. ADHD kids do need correction, but that doesn't mean their next impulse won't defy that correction.
To me, your posts implied that ADHD kids might fidget or lose attention or have a lot of energy, but not cause them to act out or misbehave and that is what I disagreed with. Perhaps I misunderstood
This kid has problems beyond just ADHD, I would wager.