>> but personally I'd like to teach my kid how a computer works, not how to use some programming language.

I wonder if assembly is a better choice... hmmm...

Well one can follow on from the other.

Assembly is add R1 R2. Forth takes the 2 numbers from the TOS and puts it in those registers. That wasn't obvious what was happening in the post, I wonder if student me would have wondered.

You could make the case for going all the way down to the silicon.

We teach English, maths, science to give a rounded understanding, not to make student productive or give them information that will be immediately useful. IT/computing in secondary school should be doing a similar thing. It should remove the mystery of what a computer is. That it is programmable. Hopefully it's improved since I was young and we were basically shown how to use Excel.