1. Food additives - glutamate for example. (AKA MSG among other names) Is used as a preservative in processed foods. But glutamate is an excitatory neurotransmitter. With the rise in processed food consumption, you cannot feed a child a steady diet of exogenous excitatory brain chemicals & expect them to sit still. Red food dye has been shown to have the same effect.
2. Lack of parenting. As another poster pointed out, some kids can sit for hours & play video games or stare at the TV, but when it comes to school, they aren’t made to apply themselves & be disciplined.
Our country is hosed.
My daughter was diagnosed as hyper-active. Our peds doc said he didn't drug kids - Moms maybe, but not kids. He recommended a book that recommended a diet, The Feingold Diet. No preservatives, no food dyes, no processed sugars. It meant no soft drinks, sweets only on important occasions, fresh or frozen vegetables. Worked great for her and for us as a family. The kids had perfect teeth. The hyperactivity was controlled. She did well in school. The kids were outrageously healthy, seldom coming down with all the stuff going around at school. The diet was a blessing in so many ways.