The right speaker and the subwoofer plug in to each other with a midi type( I think, resembles ps/2 mouse cord). The left speaker plugs in to the sub with a standard a/v type connection, the connection to the computer is a regular headphone type connection.
Except for the right speaker and sub distance from each other, I see no reason the other couldn't be extended, and you can certainly extend all of it from the audio source with an extension cable. Hope that answers your question!
If the room is regular sized classroom. I use them in a room about 140 sq. ft. And set the volume a bit over half. Of course this is assuming your second graders are pretty quiet (almost an oxymoron I know). At full volume they remain undistorted bit too loud for my taste. Good luck and thanks for your service as a teacher.