Hello, and welcome to the thread where we figure what Wishiwashis' ability Schooling actually does.
So, the trailer says the the ability starts working when Wishiwashi reaches a certain level, which is then followed by Wishiwashi transforming at the beginning of a battle. This can't just be the case, as why not just evolve it.
As we see in the trailer, the battle where Wishiwashi transforms is against a Gyardos, a Pokemon with the ability Intimidate. The thing is, we don't see it's ability activate in the battle. So, that gives me two ideas to how Schooling works.

>after Wishiwashi passes a certain level, and it's stats are lowered in battle, schooling will activate
>after Wishiwashi passes a certain level, and the opposing Pokemon's ability activates, schooling will activate

What do you guys think?