Like poles will repel. Place a bar magnet on a table at each group. Put a sheet of paper over the magnet. Sprinkle iron filings on the paper. Tap the paper gently.
Lines form to show the magnetic field.
Put another magnet under the paper. Make sure the poles are together. Tap the paper. Filings between the magnets should be veering away from each other. Change the magnets so that poles are unlike.