[zero00]

I looked at your world and I didn't see any code to make the fish or shark move.

To move all of the things in the school:
-Put in the movement code you need like "Fish move forward 1 meter", for example

-Put in a "For all together" that is referring to the "School" list

-Place the movement code you made into the "for all together"

-Replace the objects in your movement code with the "item_from_school" in your "for all together"

All of the fish and the shark should move forward 1 meter.
Make whatever changes you need!