A child held in an artificial environment will exhibit a spectrum of behavior. Add in Dietary issues and sugar abuse in particular, allergies and the odd real issue and we have plenty of causation.
Then use training that is appropriate for possibly two thirds to one third of the class and plenty of behavior issues can be expected. And just what do you hope to accomplish with a child who is reading deficient?
All this opened the door for a finding of anomalous behavior that could be treated with a pill. It felt, looked, smelled, and sounded like nonsense. Yet millions of vulnerable children are fed this pill. .