Many species of fish, particularly smaller fish, travel in schools, moving in tight formations, often with the precision of the most highly discipline

Many species of fish, particularly smaller fish, travel in schools, moving in tight formations, often with the precision of the most highly disciplined military unit on parade. Some move in synchronized hordes, while others move in starkly geometric forms. In addition to the varieties of shapes of schools of fish, there are countless varieties of schooling behaviors. Some fish coalesce into schools and then spread out in random patterns, while others move into close formations at specific times, such as feeding times, but are more spread out at other times. Some move in schools composed of members of all age groups, while others move in schools predominantly when they are young but take up a more solitary existence as they mature. Though this behavior is quite a regular, familiar phenomenon, there is much that is not completely known about it, particularly the exact function that it serves and what mechanisms fish use to make it happen.
Nghĩa của mấy từ school trong bài này là gì vậy mọi người ? Vì sao như vậy ?