How many students are there at Hagun Academy?
Hagun Academy (破軍学園 Hagun Gakuen) is one of the seven Mage Knight schools -> there are only 7 schools.
We have a rule



  With the competition, six students defeat 10 different students earning them their spot as Hagun Academy’s representatives for the festival.


So looks like we have less students in Hagun. 

BTW, it's LN logic !!!