Isaiah is a student in Wonder. He attends school at Beecher Prep, where he is good friends with Luca. Before Julian's so-called "war" when he and Luca sided with Julian, they used to sit with Jack during lunch.
On the first day of school, Isaiah was sitting with Luca during lunch when Jack came over and sat down with them. Isaiah had never met him before then, but they soon became good friends. They talked about baseball during lunch and later they all played basketball together. From then on, Isaiah, Luca, and Jack regularly sat together.
Everything changed when Julian began his "war." Isaiah sided with Julian. When Jack tried to sit down with him and Luca during lunch, they ditched him.
Ultimately, Isaiah is among the students who go over to August to congratulate him on receiving an award at their fifth grade graduation.