Sensei! Bokutachi ga Sekai wo Horoboshimasu
I am reading this one and i think he has your description..?
Though it is a fantasy world where the MC is an assassin that is now working as a teacher for problematic kids that will cause destruction in the future....
And yes, the mc knows abt this and is a teacher there to try and prevent that from happening
Tysm for the rec! I’m actually all caught up with that one too and I can’t wait to see how Class F will pull thru in the current chaps ヾ(☆▽☆)
Looking for content where the MC has dark hair and looks tired as fuck 24/7!! Would would LOVE if it was yuri but im with it being male MCS of action manhwas