Filming (video) and photography at school performances have often been the subject of rules and disagreements. I still have videos of my son's and daughter's primary school productions, (taken with my own camcorder and strictly for home viewing) and my daughter's dance class: all taken within 25-30 years ago, and they have been the source of much amusement on odd occasions since. Not long after that, there was a ban put on parents even photographing their own children in most places: all to do with Child Protection issues. Only "official school photos" were allowed (usually costly to buy!).
Some of our local schools have now done an about turn on this, having first secured the permission of ALL parents of any given class for their kids to be filmed, whether on Mummy's mobile or a big video-cam.