Whether you were perpetrator or victim you recall acts of great cruelty that were enacted in your schooling. I purposely do not separate simple observers, for even as a watcher you had a direct emotionally response to such incidents, commiserating with one or other of the parties, the poor unfortunate oppressed, or the troubled oppressor. Education is far more than the formulated reading and writing, it includes social graces and skills we carry forward through adolescence to adulthood, inclusive of the hierarchy of power. Which step we are inclined to stand upon on the staircase of authority is influenced significantly by formative lessons and experiences.
Humans do not suddenly become monsters. Those are the culmination of a continual accrual of evil, through small perhaps unnoticed acts that when grouped together create a nightmarish construct. As for monster also read victim, the process is similar, but less noteworthy and far more pervasive. The universe is full of unfortunates, but thankfully few behemoths.