>What a word-poor language you have! How about gaggle of geese, mob/crowd/audience of people, school of whales (I think there's another one for dolphins)? There's also mob (of kangaroos/monkeys?), mockery (crows/ravens/magpies?)

A bunch of whales is a pod, not a school. Only fish come in schools. I don't know what you call an amalgamation of dolphins. Perhaps they too gather in pods, since they are fellow cetaceans. The American Heritage College Dictionary defines "pod" as, among many other things, "A school of marine mammals, such as seals, whales, or dolphins" followed by a question mark for some reason. I don't always trust dictionaries to define biological terms, but these words are not particularly biological.

An assembly of sharks might not be a school. I don't know if the fact that they are cartilaginous fishes has anything to do with it. The word "school" might imply not only that several sharks are in one place, but that they are travelling together, which they probably aren't. Calling the accumulation of sharks a "frenzy" would make a statement not only about their multiplicity but also about their activity.

The same dictionary defines "school" as, among many other things, "A large group of aquatic animals, esp. fish, swimming together; a shoal."