The teachers that were in the stand, selected those that they thought were not the best choices. This was done on purpose, as they felt like if they showed some of the worst, it would then make the more talented vampires look better.
After all, this event was as much for them as it was everyone else. They wanted to show that they had talented students, and were doing well in guiding them as well. Maybe, even they would get noticed for their talents.
What also seemed to be done on purpose, was students near a similar grade, if not the same grade, were selected for the first fights. This allowed for a nice spread of students on the three platforms to be shown.
It also gave the children a good chance to see where they were at, compared to others that were the same age as them.
