Here's my take: school math past the basic arithmetic will be useless in life for the majority of people. Any non-trivial school-level-related math question can be easily solved within 10-20 seconds by a Google search.

That's also why all the examples of math's usefulness become ridiculous stories like: "imagine yourself getting stuck on an uninhabited island and having to calculate the triple integral to find the volume of a barrel of water".

No. The real use of school-level math/physics/chemistry/language is in laying the _foundation_ and training the brain.

And it doesn't really matter what exactly you want to use for mental training. Every structured activity is fine, as long as it engages the brain.

Even pointless tasks like memorizing scriptures help. There are studies that show that religious students who spent a lot of time on rote memorization, and later switch to other disciplines, in the end do quite well with their studies.