Maybe in the Delquan fanfiction, the Pokemon School has a special tournament. Ash enters it with his Pokemon. Along the way, he discovers new strategies and abilities of his Pokemon. He could also face some tough opponents who make him and his Pokemon grow stronger.
Ash could meet new friends and rivals. For instance, he might find a rival who has a completely different approach to Pokemon training. This would force Ash to reevaluate his own methods.
In the Pokemon School in this fanfiction, Ash could be involved in a mystery. Maybe some rare Pokemon are disappearing from the school's area. Ash, with his inquisitive nature, decides to investigate. During this process, he teams up with other students, including Delquan perhaps, and they uncover a plot by some villains who are trying to steal the rare Pokemon for their own evil purposes.