Yet most of the time there is considerable order with precision control reminiscent of a military parade. The vast ocean is an open classroom where 80 percent of all fish attend school at some stage of their lives, with the other 20 percent either home-schooled or engaged in self-studies. But not all who attend school receive passing grades. Some may stay in school forever, some die along the way, while others join school only for some hanky panky and then leave!
What do fish learn in school? There are five basic fish school syllabi: Life Skills; Gastronomy; Survival Strategies; Geography and Sex Education.

Generally a school comprises fish moving in a coordinated manner that are not always of the same species, but are roughly similar in size. For example snappers, fusiliers and surgeons may form large schools. A shoal, on the other hand, is more generally a grouping of fish, not necessarily the same size or species. An ‘aggregation’ is a grouping of fish where the members swim in different directions within the group, while a ‘pack’ refers only to the apex predators that congregate when there is something to feast on. Being near the top of the food chain they have no need for order or control. As a result, a pack is a haphazard ensemble with members moving in and out of the group.