Cecilia Somni and the Knights of Silversong Academy

In a place unknown to modern society lives the twin Islands, home to the kingdom of the Sun, Caelesti, and the kingdom of the moon, Noxsidus.

Noxsidus, brimming with magic and wonder, is known as the luminous kingdom of mages, as all types of magic, dark and light, are practiced. Caelesti, however, banned unrestricted magic due to a curse put on the royal family many years ago, and every mage must register themselves unless they would like to suffer in the royal dungeon for the rest of their lives.

...

Cecilia Somni was a totally ordinary girl from the backwater town of Breverden who never had many ambitions. Yet, when she was accepted as a stablehand in an elite school for knights, her one dream began a step closer: becoming a royal knight of Caelesti.

All Cecilia had to do was impress the headmistress, Ms. Silvia Song, and she would be admitted to the school! It can't possibly be that hard. Right?

While Cecilia is attempting to be allowed into knighting school, a war brews between the two kingdoms, and Caelesti is suspected of kidnapping the crown prince of Noxsidus.

...

Once accepted into the school, Cecilia uncovers all sorts of hidden secrets within the aged walls and must fight mythical beasts to prove she is worth keeping around.