Same issue with our daughter's dance competitions. The governing body has a strict no photography rule during competitions. The school organizing a given event is allowed to hire a photographer who sells images at a kiosk. The organizers get a percentage of the photographer's fee. A recent competition had staff policing iPhones. Delete the video or your child risks disqualification.
I'm happy to pay for quality photos or a DVD with video clips so I can enjoy the performance but I have yet to see an image worth buying. $15 per image, SOOC to kiosk, direct to printer.
A roller derby game I attended also imposed the same restriction. They hired a couple to shoot the game. To this day I haven't been able to find the images online. Disappeared into the ether.
I get the no flash policy. It's a hazard for performers on stage. No problem. Banning cameras entirely for misguided social media reasons (proprietary choreography and/or Internet predators) or to allow one photographer to monetize the event is frustrating considering how much we spend on these activities.