newmath School subject since the 1950's Parent-puzzling arithmetic Number theory and abstract algebra, e.g Failed school curriculum that was the subject of the 1973 book "Why Johnny Can't Add" Education fad of the 1960s 1960s educational experiment '60s elementary-school innovation Educational innovation of the 1960's 1960s teaching focus Teaching approach based on set theory 1960s educational doctrine Teaching method based on set theory Set of teaching practices introduced in the 1960s