I believe it is prudent and the obligation of the school to let parents know what they observe. Unfortunately, it is not always seen by adults. Many bullies are very astute at hiding their antics.
First and foremost,I believe a parent needs to create an open and safe nurturing environment for the child so that they child can comfortable talk to the parents about it. Parents need to ask questions about the child's day, who did they see, what happened at school. The child often wants to share but parents are too busy to listen.
It will be a cold day in he!! before I allow any school official to bully me and they had better look out if I found out they knew my child was being bullied and I was not contacted.
It is a complex issue and EVERYONE, parent, teacher, child admin, need to be open and communicate readily problems and successes of our children