As a lower-ranked academy under the super-large mage organization Mystical Blade, the Talenry Tower had very high standards for recruiting students. Most normal academies required acolytes to be able to cast one-circle magic spells before the age of 20, but Talenry Tower required their acolytes to be able to cast two-circle magic spells before the age of 18.
Although it didn't seem like that much of a difference—there's only a difference in two years and one circle—those two years just happened to be a critical growth period for humans. Without those two years, plus a requirement of one more circle, made it akin to the difference between the Iron rank and Bronze rank—gigantic. It typically took four or five years of growth to make up such a gap.
