According to Wikipedia, "any group of fish that stays together for social reasons is said to be shoaling...". Before my tank crash, I had a Sailfin, Hippo, Mimic, and Tomini tang. The Tomini tang kind of did its own thing and sometimes the Mimic would follow the Tomini around (they came from the same tank of a previous owner). However, my Hippo would always shadow the Sailfin around the and the Mimic would usually follow. Sometimes the Tomini would join. The Sailfin was definitely the king/queen of the tank so I guess this kind of made sense. Based on the definition above, I don't see why you couldn't call that a shoal of fish IMO.
The Sailfin always followed me around the tank so this video was to highlight that behavior and not so much the shoaling behavior. You can see how the Hippo follows the Sailfin and the Mimic follows the Hippo in the video. I still have the Hippo today and plan on adding the same group of tangs. I really miss that behavior. I am guessing this time around the Hippo will be the leader. Enjoy!