When I learned set theory and relations for the first time, I was in love with the abstractiveness of mathematics. It was so intuitive and I truly felt that I've got the grasp of fundamental principles of maths. The sad thing was, we were introduced to set theory in Grade 11(17 years old), that's too late IMO, it should be taught around Grade 4.

Everybody learns that at school, French or not (I certainly did in Australia). The set theory referred to here is very abstract.