Have you ever noticed hyperactive kids? A lot of parents tell me that their child is very hyperactive and is unable to focus on something for a longer time. They want to know the reason? They want to understand how they can make their child sit a little longer.
The secret lies in the “concentration span” of a child.  
In a classroom setup where the kids are taught, the “concentration span” of a child varies from 35 to 45 minutes. After that, they need a break and a change. Therefore, you will find most of the schools have a period of 40 minutes.

Self-study time in boarding school varies between 2 to two and a half hours. During self-study, kids work on subjects of their choice. You can also compare this with homeschooling.
But, have you ever seen an artist working on a piece of art? You will find they continue working on that for hours together. Why?

If someone works on their own with their interests, then the concentration span takes another dimension. Concentration is directly proportional to the interest.
So, I hope now you know how you can help your child.