16-year-old Helena Muffly wrote exactly 100 years ago today:
Friday, January 5, 1912: It’s so cold now. How quickly the weather has changed. I didn’t mind it at all in school for the stove sent forth a regular shower of heat. Was rather freezy coming home and the wind a blowing. We’ve come to the extracting of the cube root in arithmetic and I can’t see very good the way it’s done. But suppose I can after I get some kind of an explanation from somebody and not from the book alone. We had these things several years ago, but my idea of them is now rather hazy.
Her middle-aged granddaughter’s comments 100 years later:
Whew, math has changed a lot over the years.
I never learned how to do cube roots when I took math in the 1960’s and 70’s, but I can remember struggling with square roots. My children can manually calculate neither square roots nor cube roots, but they do know how to calculate them using a calculator.
Has the curriculum been dumbed down over the years? . . . or has the tedium been removed so that students have time to grapple with more complex problems?
A Hundred Years Ago 
My father, who was born in 1913, was amazing when it came to math. He could calculate double and triple digit multiplication problems in his head, and he only had an 8th grade education! I definitely think the curriculum in schools has been dumbed down.
It is absolutely amazing how people used to be able to calculate really complex math problems in their head. It’s fun to read the mental math tips and “tricks” in old arithmetic books.
I think the people with an eight grade education then knew more than the high schools graduates today.