This could be a maximum of three people. They are the ones who perform and/or initiate the bullying attacks.
Multiple classmates who participate in the attacks in a changing composition. Not infrequent, former bullying victims can be found in this group as well.
They are not actively involved, but laugh at the victim or root for the offenders or followers. Sometimes they do not properly perceive it as a bullying situation and even tend to misjudge it. (“It's all in good fun! “)
First they try to protect the victim, but hey often tend to withdraw in fear of becoming a victim themselves.
This includes classmates who passively observe the event and are afraid themselves of becoming victims, and therefore remain silent.