Kids are learning when they are challenged. In this example the problem is open-ended. After what turns out to be the first round even the best performers can improve. And those farther down have the chance to improve.
I am now reading:The man who knew too much by G K Chesterton - a different kind of detective.
Autobiography of Mark Twain by Mark Twain aka Samuel Clemens. First volume. It's not structured, jumps from 40 years ago to yesterday. Very interesting
Trespassing on Einstein's lawn by Amanda Gefter - Journalist who was not at all a scientist took on the big questions. And became a first-class science journalist. Stalled right now.