The central claim to measure reason is that, contrary to public opinion, the psychologists who dominated educational policy making between wars were educational advances and political extremists. They argued that education should reflect the needs of children rather than the well-being of adults, and that intelligence testing was considered to be a tool for child-centered learning.

These psychologists owe their political inspiration to the ideal of merit and popularity lost with this diminishing ideal after the war. There are four main themes that dominate the discussion: the emergence of educational psychology as a distinct system.

The modern history of ideas on the mental development of children; the role of experts in the formulation of educational policy; and the rise and fall of merit measurement.