I put no for school, but we can for the nursery.
Well we can take them of our own child, but that's impossible at Sports Day or on stage, you always get another child which isn't allowed, reason being is our school has had children under Social Services in the past (might even still be some now for all I know) and HT takes no chances as a few years ago two kids were at the school and there mother wasn't meant to know where they were, she found out and went ballistic at the school, terrifying two classes as she thumped on the door and windows. Staff can take photos during the year of kids whose parents/carers have said it's ok.
It is annoying, but loads of parents do it anyway, they just don't get caught!
Nursery is fine as teachers know every single parent and there are no care orders. No doubt that will change if there are in the future.
Our swimming pool has a no photo policy, fine when the kids are in with general public, but completely obscure when it's a private pool party and every parent has said it's fine to take their kids pics!!