To demonstrate the force at the poles: Suspend a bar magnet by a string tied around its middle, so that it hangs in the air. Unless it is affected by nearby strong magnets, it will turn so that one end faces to geographic north. Use this fact to label the pole N and the other S.
Approach the poles of another magnet to the N or S pole of the hanging magnet. The pole of the hanging magnet will turn in response, moving toward or away from the test magnet pole.
The magnetic field can pass through non-magnetic materials.
Students will easily find that a magnet can attract magnetic objects through a sheet of paper, a paper plate, a sheet of plastic, etc. A magnet under a piece of paper can be used to make a paperclip move on top of the paper without the magnet directly touching the paperclip.