I'll always remember that moment on RPG maker (probably around 9 years old) where suddenly I've understood Variables (I was experienced with HTML and so-on prior), a whole world was unlocked, VB6 programs became possible, everything "clicked" suddenly. I feel once you understand the fundamentals on how it works, it's easy to progress very fast as a child/teenager afterward.

With my kid I want to ensure that fundamentals of computing are understood as early as possible, this is what allows you to understand how the world is interconnected.

I similarly remember struggling with understanding what "classes" were in PHP as a kid and why on earth they'd ever be useful for, seems like needless abstractions, but finally it clicked, and a whole world opened up, suddenly I could understand much more of Zend Engine than before, and software engineering became a thing I started caring about. Of course, later I was enlightened again so now I avoid classes.