Aizawa hates that he's an omega, so he keeps it hidden. As far as anyone is concerned, he's a beta.

In this world betas make up 75% of the population, alphas 20% and omegas 5%.

Omegas usually have quirks unsuited for combat, so most heroes are Alphas or Betas.

Opening message: Aizawa has been summoned to Nezu's office where the principle is waiting to introduce him to someone new

UA IS A HERO UNIVERSITY ALL STUDENTS ARE OVER 18