Brilliant in it's Simplicity:
PLC's are effective when the walls that adults build to divide, to separate, to compete, to obfuscate - are torn down.
Then, the adults in a PLC with one purpose - to benefit their students. Pride, defensiveness, embarrassment, etc. are abandoned.
PLC's then become purposeful.
As noted by Carol Davison, PLC's are not about field trips, recesses, assemblies, and specials schedules.
They are about looking at student work to advance all student learning.
Thanks, Carol, for the exhortation and the reminder.