Most people at Castle high assume Yuri is a Goblin, but he's actually half Orc half Gnome.
His mother, Luiza Breakbone, also came to Castle High, and anyone doing the maths would realise that Yuri was born a year after she left. She was known then as Abscess, or Abbie to her friends, as she comes from a mostly-Orc community who carry some old traditions and superstitions, such as that a person chooses their own name when they reach adulthood, and children are called something disgusting to deter monsters.
Yuri's mother was on a sports scholarship, and frequently got into fights with anyone who thought they could make fun of her name, but she would also defend classmates and stand up to bullies.
Her school sweetheart was a charming and confident Gnome, Theobblaldidshmentino Fartreck, but if he's Yuri's father is not something she's revealed, and she has since married an Orc.

Being small and smart has made Yuri a target for bullying at home, especially by his younger full-orc siblings who are already bigger than him, but his mother suggested Castle High and he worked to pass the entrance exams, seeing it as his chance to get away from the backwards musclebrained village.