The problem is that the public school environment is not reflective of real social engagement at all. You aren't forced to spend years with the same people without recourse like you are as a child, your time is not controlled as astutely, and your options to disengage with people you don't like is nonexistent.
Its why school bullies often end up totally dysfunctional in adulthood and end up drug addicts, because they can't compel anyone else to be around and stay around them while they are abusive. Some "luck out" and can find someone emotionally damaged enough to exploit, but then they just abuse an already damaged person in near isolation - there isn't a "cool wife beaters club" for them to hang around at the mall with.
You largely get to choose your peers in adulthood. Sometimes that means you have to live somewhere else, find a different job, maybe even move to a different city or state to escape an incompatible culture. But having that choice alone radically changes the dynamic enough that all the "tough skin" and social paranoia you have to develop to survive most public education systems is inapplicable and often harmful to have in adulthood.
Women develop a thick skin just to endure years of spousal abuse. Men don't express themselves and develop deep psychological complexes and overwork themselves to the point of self harm.
The public school environment is a far cry from an optimal environment to develop social skills in. I'd go as far as to argue it contributes somewhat to why the top post on HN right now is an 800 comment thread about pandemic loneliness. You don't get to deviate in public school much - either the authorities will punish it or your peers will ostracize it. And kids learn to cope the same way abuse victims do by suppressing the bad feelings and developing resultant mental illnesses and lifelong emotional complications.