There's a considerable difference between schooling and shoaling. Schooling fish like Tetras, mimic one fish's movements and they do this so aggressive fish believe the school is one larger fish. This is for protection. Once a group of schooling fish feels comfortable in their environment, they'll no longer school. Shoaling fish like Corydoras, forage in a rough group, but their movements are individual.
Schools are 8 or more. A shoal is roughly six.
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