If it starts on school property (or other school function), then yes. Otherwise, no.
Basically, if someone secretly videotapes another student at school, and then posts it online for others to make fun of, then it is the school's responsibility to protect students from that.
How can the school do anything in that situation to stop it from happening? It's "secret".
I meant if the victim (or ally) shows that the videotaping started at school, and tells the school, the school should discipline the bully.