A Mathematician’s Lament by Paul Lockhart (also referred to as Lockhart’s Lament): https://www.maa.org/external_archive/…​

The essay has been expanded into a book of the same name: https://amzn.to/2OvaBGl​
Paul Lockhart has also written a book showing how math should be done: https://amzn.to/3rFSqvz​