The Server is the heart of Space Battle Arena. It is a graphical client and portal to the universe. It handles all data from clients (student's ships) and displays their locations in the world.
Currently, it is available as a Windows executable (or via Python source on GitHub), see the links above. It should run on Windows 7 or above. See Mac OS X Server from Source for info on compiling on Mac.
It is recommended to run the server on a machine which can project to the entire classroom so everyone can see it. Every machine in the classroom should also be on the same subnet, otherwise you may have issues with clients connecting to the server.
Look to the other sections on the left, to dive into a bit more about starting and operating the server.