The Ability Schooling will not take effect if Wishiwashi is below Level 20 or if it's below 25% HP. Healing Wishiwashi will also revert it back to its Schooling Form. The Ability cannot be disabled, but it can be avoided. Also note that the Ability-suppressing move Gastro Acid and the Abilities Mold Breaker and Neutralizing Gas will not affect Schooling.
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Mold Breaker (Serebii) Gastro Acid (Bulbapedia) Neutralizing Gas (Bulbapedia)
