I remember talking with the mother of a child with ADHD. She recounted interaction after interaction with his school, many not exactly turning out as desired. My response was simple: "Run him." At least in my experience, physical activity is the easiest way to get, say, a puppy or my kids, or for that matter myself, to be calm in both body and mind.
As it turns out, research at the University of Central Florida (UCF) verified that off the cusp reply: kids with ADHD in particular learn better when they're squirming. More specifically, physical activity like fidgeting and moving hands, feet and legs helps in learning, reasoning and comprehension [article].
Physical movement was actually most pronounced when kids with ADHD needed to use their brains' executive brain functions including working memory (which they measured). “What we’ve found is that when they’re moving the most, the majority of them perform better. They have to move to maintain alertness.” explains Mark Rapport, an author in the study and head of the UCF Children’s Learning Clinic.
According to Rapport, "facilitate their movement so they can maintain the level of alertness necessary for cognitive activities.” If you can make it work for your family, I suggest that this is superior to (much more expensive) pharmacological intervention.
The mom I was talking with? She got an exercise bike for her son, and it worked.