Children with ADHD are able to retain information which they use on a daily basis, but they often have difficulty with what's called working memory, i.e. the updating or mental rearrangement of information in the mind.
New research in the US looked at what would happen if hyperactive children weren’t told to sit still, and how it would affect their working memory.
To their surprise, they found hyperactive movement specifically helped working memory. This insight would be difficult to apply at school, but it’s worth a try at home.
Read more on treatments for ADHD