Dampen an all-purpose, heavy duty melamine foam sponge, such as a Mr. Clean Magic Eraser. Rub the sponge over the marker to remove it from the surface of the locker.
Soak a clean cloth with rubbing alcohol. Hold the rubbing alcohol-soaked cloth over the marker to lift the stain.
Place white toothpaste on a bristled cleaning brush or toothbrush. Rub the toothpaste onto the marker to loosen it from the surface of the locker. Use a clean cloth to wipe away the marker.
Spray hairspray onto the marker. Allow the hairspray to sit for a few minutes. Wipe the area clean with a clean, damp cloth.