About 150 years ago, the Western world, in the midst of a major industrial revolution, began an experiment. It started gathering all children during weekdays into rooms where teachers told them what they should know: memorizing letter symbols to read and bits of knowledge to recite and repeat on tests. Learning was rewarded in various ways.

Soon the rooms contained only children of a single age, because it was more efficient. Learning had never been like this before. Previously for most children, learning was (and still is) done by apprenticeship, often one-on-one, with children observing adults who tutor them to gradually take over the tasks. Children's rewards lie in accomplishment of the tasks.