While one could easily complain at the quality of science fiction that might be on television at one moment, it cannot be argued that there has been a lot of good science fiction over the years. As a teacher, short videos that last a period are great tools for instruction and television shows fit that bill pretty well. I wanted to give a quick list of quality science fiction shows that you can pull from. Some are appropriate for middle school ages but others are more edgy and appropriate for high schoolers.
The Twilight Zone was a series of short shows, each lasting approximately 23 minutes. These shows, each one with a different cast and story, were always a complete more tale told within the confines of a short science fiction or fantastic environment. These shorts are often very well written and highly appropriate for both middle school and high school. You can buy the DVDs, but many of the original episodes are available for free to watch on Hulu.com.
The Outer Limits was a series of strong science fiction shows that were on at approximately the same time as The Twilight Zone. The format was similar but the stories were an hour long and the themes were a little more science fiction-based. If you could call The Twilight Zone science fiction lite, The Outer Limits was science fiction full-body. As well, The Outer Limits were less based on morality than The Twilight Zone (which could get a bit tiresome), instead putting the emphasis on the story ideas. There was also a more recent Outer Limits series, filmed in color, which is also available on Hulu. The older episodes are readily available on DVD.
One cannot discuss science fiction on television without mentioning the king of all science fiction franchises, Star Trek. While the original series (ST:TOS if you're a geek) played for only three seasons from 1967–1969, since 1980 there have been four other Star Trek TV series based on the original show, twelve movies, and a little-known animated series from the 1970s. The premise is simple: a star ship travels from solar system to solar system, encountering new civilizations and dealing with moral and science fiction-type problems. The exception to this was Star Trek: Deep Space 9, which took place on a space station. While the show could suffer from bad writing, especially in the later series a certain type of bad writing called technobabble, Star Trek was also remarkable for its ability to express science fiction topics to a mainstream audience. While the movies were more adventures than explorations of concepts, they also could be loads of fun for viewers, except when they were very, very bad. To be safe, stick with showing the popular episodes. A good list can be found here, but for my money, show the episodes “The Doomsday Machine,” “The City on the Edge of Forever” (with Joan Collins!), “The Trouble With Tribbles”, “Balance of Terror”, and “Arena”.
The television show Battlestar Galactica has an odd genesis. It was originally aired in the late 1970s with a promising premise, the remains of mankind fleeing from their enemy on a fleet of ragtag space ships, protected by the last remaining warship, the Galactica, from their enemies the Cylons in a quest for the legendary planet of Earth. Unfortunately the show never lived up to its promise and was more cheesy and silly in the special way only art from the 1970s could be. That said, the special effects were excellent, and the show did develop a cult following. In 2003, Ronald D. Moore and David Eick reimagined the series in what has become one of the most successful reboots of a series ever. This new series took the sad premise of genocide seriously, making the series one of the most effective television dramas ever filmed. The Cylons became, instead of an alien species, an artificial intelligence made by the humans, a sort of Frankenstein's Monster returned to destroy its creator.
One of the things that made Battlestar Galactica successful was the fact that it posed a dark scenario for the survivors and did its best to portray how humans would react to it. They make bad decisions, people get killed (including major characters), difficult compromises must be made, and through all this the people must survive. While this show is mature and suitable for high school students, it's a fabulous example of ambitious science fiction. As a recommendation, watch the series opener, the first episode (33), and the beginning of season three. The season three episodes were ambitious in that they posed a situation like the Iraq War making the humans the “Iraqis”. Most of them were living on a planet and were captured by the Cylons, putting the humans in the position where they're becoming urban rebels, suicide bombers, and terrorists. This turn of events was even more powerful because it was broadcast while the actual war was at its height, making it a powerful editorial on the conflict.
There are other science fiction series which can be discussed, but these are a good jumping point. Other suggestions are Babylon 5, Stargate SGU, and some of the later Star Treks, especially the best of the Star Trek, the Next Generation episodes.
I find television to be an effective way to explain science fiction concepts in a short package before I introduce the class to the actual novel we'll be teaching. That way they can get comfortable with the fact that the plot is about an “idea”, instead of being just a storyline.
Incidentally, the original Star Trek episodes were recently remastered with an update of the special effects. While remastering of classic shows can lead to some disasters, for a good example of that check out the “Han Shot First” controversy from the remastered movie Star Wars: A New Hope, this remastering just improved the low-budget 60s-era special effects. Episodes are available for individual purchase on iTunes for $2.00 each.