Can I yell at my fellow parents in the audience at my daughter's school concert because they won't put their phones down?
Why does it bother you so much if they use their phones?
Because it's rude to the children who are putting on the concert! Pay attention so the kids feel proud of what they did!
It's not polite to yell at people or cause a scene. Doing that will just disrupt the performance and embarrass your child. I understand being frustrated by people using their phones during the concert, but they may simply be using their phone to record it.
But the kids worked hard on this and parents are being rude!
That may be true that they are being rude by using their phones during the concert, but yelling at them is also rude and more disruptive than the parents using their phones. Just ignore them and focus on watching the concert so you can enjoy seeing your daughter's performance!