This article is a socio-historical account of the development of the Attention Deficit/Hyperactivity Disorder (ADHD) diagnosis and methylphenidate treatment in America, attending particularly to the political and institutional contexts that have supported this development. Historical developments in early-mid-twentieth-century America frame a national analysis that views contemporary schools and schooling practices as mediating factors in ADHD diagnoses and methylphenidate treatment. Consideration of the school as a mediating cultural context illuminates important questions about cultural variation in tolerance of young children's behaviour, educational and behavioural goals for children, and cultural styles of treating problem behaviours in children. It is argued that cross-national research on schools and schooling would increase understanding of the complex national and cultural features of pathways to ADHD diagnosis and methylphenidate treatment. (Contains 1 figure and 4 notes.)