EAG@IOE: Why were external national exams decided upon for 16 year olds in England and Wales?

This talk presented policy thinking that went in to the creation of the national assessment system in England and Wales, going back to the first government sponsored examination system for 16-year-olds (the School Certificate) and moving on to its replacement by O levels in 1951. Why was it that the system chosen was for exams to be externally provided, a pattern which has survived for over 100 years? The talk presented historical examples of policy making and the complexity of such decision making.