Elsewhere the suggestion was made that Heinlein's Juveniles were not, in some way, valid, or maybe relevant is a better word, any more because, "children aren't like that any more."
I don't know about that. My daughter, age 9, loves them. It started when I read them to her in installments a year or so ago as "bedtime stories". She kept saying "More!" and I kept having to insist "No, it's time for you to go to sleep, sweetie." This year, she has a school reading assignment where she gets to pick a book, read it (10 pages at a time for the assignment), and write something about what she read. She picked Have Space Suit Will Travel. (Finished that and went to Piper's "Little Fuzzy" but that's another story. She wants the other Heinlein juveniles but I only have the one in dead tree at the moment. The rest are in e-format only.)
I don't think it's so much "Kids are different today" as it was more OK then to write about exceptional kids, ideals to aspire to rather than the mush of "everyday life."
And, as it happens, "Have Space Suit, Will Travel" remains my all-time favorite book--not just science fiction, not just juvenile, not even just Heinlein, but book.
To emphasize, even when I was growing up, the kids in Heinlein's Juveniles (or in the Tom Swift Junior books which were among my first introduction to science fiction) weren't what I was. They were what I wanted to be. And I wanted to be that because they showed me something better, something worthy of being.
Maybe I'd never acquire a space suit of my own, but man if I did, I certainly hoped that I'd be as hot as Kip at getting it working and maybe, just maybe, that would get me into space.
There were no "junior" let alone "senior" prizes for rocketry back then* but even so I tried to be like the kids in Rocket Ship Galileo because, well, they were kids doing things worth doing.
And there was no "Space Patrol" to join, and chances were I'd never be able to make the cut if there were, but oh, how I wished there was so I could at least try.
And so on. These people did things, made things happen, and sometimes . . . saved the world.
*As it happened, years later there was a prize, something that probably would have been one of the "senior prizes" in the world of Rocket Ship Galileo, the Ansari X Prize. And, as fate would have it, it would appear that I actually helped make that happen.
And so let us end once again with a musical interlude: