Science Fiction for kids--a new page I just made

Over at Educating Alice today, I saw that she had compiled a list of middle grade science fiction titles, and asked for suggestions for others.  This inspired me to go through all 1994 posts that I have written and pull out all the middle grade science fiction books I've reviewed....

And now they have their own page.

As usual, I was left wondering why there aren't more sci fi books being written/published for kids.  Specifically, why aren't there more sci fi books about robots for 10 year olds? Why isn't there more cryptozoology?

And, also as usual, I am left pondering the fuzzy nature of the boundary between sci fi and fantasy.  For instance, I've never understood why A Wrinkle in Time is considered sci fi, or time travel, by so many other readers (that being said, I just parsed my feelings in a comment below, and conclude that since they are traveling to alien planets and meeting aliens, it is clearly sci fi!  though it will always feel like fantasy to me...)  Likewise, there are probably books on my list that others would say weren't sci fi at all!  So much easier, but perhaps less helpful, to use the catch-all term of Speculative Fiction.