Six years old when they start school are expected to focus for 10-15 minutes. Kindergartner loosing attention after 5-10 minutes sounds to be exactly where he is supposed to be.
Yes, that's my opinion as well, but there is a lot of variation in the same age group. That number was pulled out of my ass btw, I only observed the differences while being there as a volunteer for various activities and from my wife's stories. And because of this variation, I think people are too eager to diagnose children with ADHD. And this is also a pity, since there may in fact be children with real problems that can't be separated well from children that are simply being children.