Childhood is often seen as a time of freedom of imagination, of unlimited possibilities. Developmental psychologists talk about "magical thinking" as a normal of stage of child development. So SF, as a literature of the imagination, of unlimited possibilities, is uniquely suited to children's literature.
Children's SF has been so common, and so popular, that SF itself is often (explicitly or implicitly) considered as something adults "grow out of." (It has even been said that "the Golden Age of science fiction is twelve") (No one seems to know who originally said this--Isaac Asimov, Theodore Sturgeon, Terry Carr, David Hartwell...?)
SF's focus on the future, as well, is ideally suited for young readers. There are some very good reasons for this. For children, pre-teenagers and teenagers, the future is a subject of intense interest. All of childhood, in fact, is a preparation for the future, and the idea that different futures are possible, and may be tested and imagined, is one that young people find easy to understand and connect to. For many lifelong SF fans (and some SF writers--and working scientists), their first encounter with SF occurs in childhood. And for many fans, SF helps to keep the open and freely imaginative childlike self alive throughout their lives.
Some fans, writers, and teachers even believe (as I do) that SF is an especially excellent tool for teaching. Some people think SF is the best(or one of the best) kinds of literature for children to read. There's even an active campaign "aimed at using science fiction literature to help turn on our nation's kids to reading, excitement and wonder."--Check out the Reading for the Future website
SF, then is often for children, but even in SF written for adults, there is a focus on children as characters and protagonists which is unusual in other types of literature. Children, perhaps, are the ultimate aliens among us. They are different, unpredictable, and sometimes dangerous. And to children, adults are even more alien, in some of the same ways.
How do you feel about what young people should read? Is SF a good thing for children? Do you remember what kind of stories you most enjoyed as a child? Go to the discussion board and discuss.