Cheep-Cheep School

Cheep-Cheep Schools are groups of Cheep-Cheeps first appearing in New Super Mario Bros. Wii. Cheep-Cheep Schools are composed of yellow Cheep-Cheeps that are (besides the color) identical to normal Cheep-Cheeps, and can be defeated in exactly the same way: Fire Flower, Ice Flower, and Starman. They are not hard to get past because if Mario, Luigi, Blue Toad or/and Yellow Toad comes near, they split into two groups, allowing the player to swim through them without taking damage.

These fish seem to resemble the beta Cheep-Cheeps of Super Mario Bros. 3.