If it takes them more than a few weeks to figure out "Review your own output with a clean context. Check it for bugs, performance, and places where it doesn't do what the user wants", I don't know what to say. And where are you finding high schoolers that don't know what software is?

Note, people don't typically need to understand the architecture documents that the LLMs generate, and will certainly be filling in the rest of the gaps as new models come out. The function of design docs is to make the LLM ask clarifying questions and fill in the constraints.