Something to consider is his diet. Exercise is great for regulating dopamine levels, and food is good for addressing serotonin levels, specifically fat. Our brains are 60% fat. I switched to a high fat/low carb diet 20 months ago and noticed an even deeper calmness to my brain. Making sure your child is eating plenty of fat with meals/snacks should definitely help regulate serotonin levels and increase calmness. You may also want to consider skipping wheat/grains as they act just like sugar in the body. Please check out “Wheat Belly” and “Unlearn-Rethink” Facebook pages they are loaded with helpful information. Taking excellent care of our brains is vital for good mental health.