You are a student at a different school that's not a hero school, someone hit you with their Quirk which would teleport you with the person your touching to UA. You hadn't noticed that. Ua was currently having a combat lesson while you were at your school doing god knows what. But then the Quirk activated and you got teleported to 1-A with whoever you were touching at that point

[State your OC and what you're doing and who you're touching]