If it's a teacher's job to get a student ready for the real world, what business does he/she have to be teaching books that, on the surface, have little or nothing to do with reality? Why teach speculative literature? This is a valid question, and the answers may be surprising. It might make sense to address fantasy and science fiction differently because, while they both share a certain “unreality”, the genres deal with very different issues.
Science fiction is the literature of the possible. It is a literature that (at its best) examines trends in technology, science and society and extrapolates what might be a result of that literature. It is literature, I like to say, that asks a “What if…” question, then proceeds to answer it.
Of course, this is a description of good science fiction. There's a lot of bad literature, cinema, and TV out there too which has little to say beyond offering a brief, entertaining diversion. The good stuff is what we want to pay attention to as teachers. The science fiction author Theodore Sturgeon is famous for saying:
“I repeat Sturgeon’s Revelation, which was wrung out of me after twenty years of wearying defense of science fiction against attacks of people who used the worst examples of the field for ammunition, and whose conclusion was that ninety percent of SF is crud. Using the same standards that categorize 90% of science fiction as trash, crud, or crap, it can be argued that 90% of film, literature, consumer goods, etc. are crap. In other words, the claim (or fact) that 90% of science fiction is crap is ultimately uninformative, because science fiction conforms to the same trends of quality as all other artforms.” (Venture Magazine, March 1958)
In other words, 90% of science fiction is lousy, but then again 90% of all art is lousy. As teachers, we have little time to waste with bad science fiction, so we here will stick with the good stuff.
Getting back to the “Why we should teach science fiction” question, there are few forms of art that address our contemporary society and its needs like science fiction can. We live in a science fiction world now. We live in a world where technology is allowing people to do extraordinary things, and science fiction is the literature that deals with the consequences of what we're creating. When the Baltimore-Washington telegraph line was opened in 1844, Samuel Morse's first morse code message was “What hath God wrought?” This quote from Numbers 23:23 asks us all, what kind of world are we making with our technology? Science fiction is a literature that attempts to answer that question.