Formal education resembles agriculture. Agriculture greatly reduced the diversity of the human diet. Before agriculture, a person might have eaten 80 different foods each week; after agriculture began, far fewer. Agriculture caused a big decline in health because its fundamental assumption – it is okay to eat a small number of foods – is false or at least very hard to reconcile with nutritional requirements. Likewise, formal education (classrooms, lectures, textbooks, etc.) surely reduced the diversity of what was learned, how it was taught, and how learning was measured.
From Diversity in Learning
Seth Roberts in Ideas That Matter Quarterly, a publication honoring the civic and theoretical work of Jane Jacobs.