Zach was about to take a lap and look for the members of his club when he realized that it wouldn't be that simple. Before he could fulfill his obligations to the city, he had to fulfill his obligations to the Academy. He had classes to attend.
So, he instead took a lap around the Academy until he found the classroom he was supposed to be in. Everyone in the class was present except Rierdan, Nessa, and Julius.
As Zach arrived, a realization dawned on his classmates.
All of those who were missing had gotten close to Zach in some way. Even in the first year, during the field trip, Rierdan and Nessa had been part of that initial tiger-hunting expedition. And Julius was one of Zach's best buddies.
The only thing that set them apart from Dukiel, Anerias, and Violina was the strength of their familiars. Considering they were the only three A-ranks in the class, it was understandable they remained.