i have a comic in my head that i've been thinking of lately and it's been so long the details are not great so i don't think i'll get any luck but i'd figured i'd ask. it was the first korean comic i read, it was around 5 years+ ago i believe. it revolved around bulling. it was extreme bullying, super physical and abusive stuff. i'm pretty sure it was in the manga format rather than webtoon because i didn't know about the resize button. the one specific point i remember is there was like a secret base of a cluster of lockers and one locker had a hole cut out of it as a secret entrance... yeah, i know it's not a lot to go on
Maybe this one?
White Angels Have No Wings