I've been looking everywhere for even a short summary of the content of the 1960s New Mathematics Math education reform in the US but I cannot ;-;
Does anyone know?
Perhaps the primary source would be the documents created by the School Mathematics Study Group.
Some films made by the group are found here.
(For context surrounding the "New Math" reform, see "A Brief History of American K-12 Mathematics Education in the 20th Century" by David Klein.)