ADHD my ass. Many of those children diagnosed with ADHD who have problems doing their homework can stay all day and night sitting in the exact same position leveling up their character in a MMORPG game and even forget to eat and go to the toilet. So they don't have a problem focusing, they have a problem focusing on boring stuff that are not natural for a child to do in the first place. Some children are more sensitive and feel more boredom than others and their mind wants to block it. But it's a normal child thing. If that happens it means that you need to change the education system to make it more interesting, not to prescribe dangerous and unnatural medications.