why is a group of fish called a 'school' ?

Some fish tend to swim in groups in order to protect themselves from their predators. the collective noun which denotes such a group depends on the species of the fish in the group,as exemplified by the terms a troop of dogfish.,a swarm of eelsand and a glide of flting fish. the most common collective nouns for a group of fish in general are school and shoal. both the words have evolved from the same common Dutch root schole meaning a troop or crowd.collected fromtimesofindiadaily.