Car simile (again?)
"Do all car owners know how their car works?"
No. In fact, from what I can see, most car owners don't even know how to drive.
However, most hackers (real meaning, not media version) know how cars work. For example, I machined a new cylinder head for my race Datsun 510 ... The stock version has the intake & exhaust on the same side, so I decided to see what would happen if it had a cross-flow head. Result? 70HP over stock. The Mikuni carbs, better exhaust & two plugs per cylinder helped ... Although I liked the Buick 215ci V8 in it better (That's the Rover 3.5l V8 to you brits).
This "Scratch" thing is a toy, not a programming language. If you teach a kid that this thing IS programming, when they first come into contact with a real programming language, they will run away shrieking ... Like it or not, computers are NOT easy to understand. They have a learning curve. Sometimes I think that Apple's "ease of use" myth has set back the GreatUnwashed's understanding of the reality of computers by several decades.
And FFS, do NOT teach kids BASIC as a first language! Instead try Lisp, or Smalltalk, or Scheme or similar ... At least give 'em a boost in the right direction!