From Experience (Score 1)

I took a reading class in high school and got to choose my own books. I picked up a "Ray Bradbury's Complete Works" and read and reported on it until my teacher told me I needed to branch out. I agree with some of the comments above about real world lessons in sci fi, and have integrated some of that into my own teaching now (as a college CS teacher), encouraging students to respond to movies that portray computers/AI/robots, etc, and how it makes them feel about technology and technological advances. Some books I think would be appropriate at high school level: Ray Bradbury short stories - good for "potential future" discussions, quite often. C.S. Lewis ("Out of the Silent Planet" and "Perelandra") - I like these because they remind me that what's really out there is nothing like what I expect. Douglas Adams and Piers Anthony - I lump them together because they don't have a lot of "speculative fiction", but they almost blind you with "what makes fantasy fantasy". Plus, they're fun. Isaac Asimov - Especially "I, Robot" for good discussion about the direction of technology (and for an easy movie day - bonus points for answering the question, "Does the movie really accurately portray the spirit of the book?") and "Foundation" if you want to get into discussions about sociology and other philosophical topics (although it might be a harder read).