Schools are group of small fish that come together. If an entire school is eaten by you, you will get a School Bonus. If some of the fish are already eaten and you eat the rest, you will not get a School Bonus. Boxfish come in schools but each shool will have all boxfish the same color. FIsh in schools never swim far from each other.
Fish that come in schools are:
Herring Orange boxfish Minnow Red boxfish Tuna Poison minnow.