Close down the public schools.
If ADHD goes away, it's not a real "disease." It's the schools that are the disease.
Another way is to get rid of almost all female teachers. They're the ones hallucinating boys have ADHD because they don't act like little girls.
ADHD didn't exist when I was a kid, because we had male teachers who let us for outside for recess - which kids should have at least once, maybe twice a day.
Were I student today, I would be diagnosed with Attention Deficit Disorder without Hyperactivity (aka "daydreaming"). I was bored with school, which is a combination of prison/daycare/military school.
I learned a lot more on my own, wandering around on weekends looking at toads and wild bamboo and snakes swimming in the local lake. And checking out books on history in the library. Oddly (I being ironic here) I didn't have ADD outside of school.
I've also found I can concentrate better after a lot of physical activity. It calms me down and I feel more peaceful and focused.