It is a metaphor, and as such, has it limits. Of course there are better ways to exercise your brain than calculus. That is just a way. Is the best? I don't kno

It is a metaphor, and as such, has it limits. Of course there are better ways to exercise your brain than calculus. That is just a way. Is the best? I don't know honestly. I personally found algebra much more interesting as a brain opener. Basic ideas of calculus come up everyday in life: interest rates, credits, statistics. If you want to understand some physics, it is very useful. Can you understand physics without derivatives? Yes, but not as good as with them. Like everything is a compromise. One possibility would be that each person has a couple of teachers that go with him/her in a way or learning specifically tailored. The other extreme is to teach absolutely the same thing from 1st grade until graduate to everybody... the compromise is to separate it in primary/secondary/tertiary education and let choose paths. Everybody will have to learn things that will never be used "in life". We have to get over it.