In the early '70s, there was a global movement in math pedagogy that took this angle to elementary learning.
Instead of arithmetic, first graders were taught set theory. Elements and unions became the first mathematical concepts introduced to 6-year-olds.
In the US, I think they called it "New Math". Here in Finland, set theory was included in the national educational system's grand redesign. Regardless of country, set theory as elementary math seems to have gone out of fashion as quickly as it gained traction, and by the early '80s was out everywhere.
Maybe, if they had stuck with it, we would all be using Haskell now as a side effect :)
(Here's a picture of a very '70s styled Finnish math teacher doing set theory: http://1.bp.blogspot.com/-vWW22FRIdfc/TobxIw3xF3I/AAAAAAAAHa... -- "Now tell me children, what is the union of green swans and red bears?")