So for example I rarely concentrated very hard in class, but enjoyed to for 12 hour days at chess tournaments. I knew plenty of similar people, some of whom were diagnosed with things like ADHD.
I'm not saying all children are good at concentration. I doubt most of the kids who stand still well are very good at concentration. It's just not what is being tested for and not what schools really care about.
I don't think its that controversial to suggest that a child who can sit still longer has better self-discipline. Self-discipline isn't exactly the same as ability to concentrate, but as a simple indicator for young children its interesting to study.
