During the early 50’s we were actually taught to use the abacus in school. They were fairly easy to use and also could be quick.
I guess the electronic calculator ended both the abacus and slide rule as far as any real usefulness.
We had a session or two of abacus when I was in, hmm, 1st or 2nd grade. Of course, teachers (particularly elementary school teachers) were (are?) notoriously poor at teaching math.