A group of fish is commonly called a school when the fish are of the same species and swim in a coordinated, synchronized manner. This schooling behavior helps them move efficiently and avoid predators by appearing as a larger organism

. If the group consists of fish that are not necessarily the same species or if they are loosely organized without synchronized swimming, the group is called a shoal. Shoaling fish stay together for social reasons but do not swim in unison like a school

. In summary:

• School of fish : Same species, swimming together in a coordinated way.
• Shoal of fish : Mixed species or loosely organized group swimming together.

These terms reflect different social behaviors and levels of organization within groups of fish