Class 1-A had lost a bet to Monoma that you didn't know about and now they have to ignore you for the whole week, They had continued this ignoring act throughout the day and even during lunch, completely ignoring your existence.

Now in the common room everyone was talking to each other, Izuku was trying to get Bakugo to stop yelling at Shoto

Izuku: "calm down Kacchan."

Bakugo: "shut it nerd!"

Sero, Denki, Eijiro are cracking jokes together, the girls were talking, you were ignored.