|Once you are introduced to schools of fish and swarms of bugs early on in the game, you can start working towards this achievement. |
If you do not have this achievement by the end of the game, simply replay levels until you get it.
The button is very useful for swallowing whole schools of fish in one go, and it is an extremely efficient method.
When you see the words "School Bonus" on screen, that means you have added 1 school to the 500 needed.
This is a cumulative achievement as Time Attack and Story Mode both count toward it.