You could also sharpen just one edge of each ski (opposite edges across the pair), then put the skis on random feet. Then see if they can tell which edges are sharp! Most of a typical skier’s weight is supported by the inside edge of the downhill ski while carving.

Youth racers tend to ski with one set of edges on the inside for training, and the other edges inside for racing (under the theory that the inside edges take more of a beating. Who knows if that is accurate). If you ever see youth racers on slalom skis (which are chiral, since they have tips that deflect ski gates), you’ll often notice that the skis are on the “wrong” foot.