Interesting topic, Green hippo.
I have always found stickers/ reward charts very difficult to use successfully both in the classroom and at home. ( I probably never did so at home anyway). Some children are very easy to reward and I did not like feeling I was rewarding them for behaviour that came naturally to them even if it was the desired behaviour of the group. I felt it set them up as superior to the rest and I was worried that their peers might resent them with the perpetual reward and awareness. It was also difficult not to reward them when they were obviously displaying the required behaviour.
For other children, the reward of a sticker was almost impossible as try as hard as they might they could not achieve what was really required...thinking children with EBD behavioural traits here and to reward them and not others would have been difficult. The reward of a sticker did not really reinforce any behavioural expectations for these children either.
Little children focus on the moment, Im being good now so I need a sticker rather than I need to do that sooner/ quicker to get my sticker.
Stickers can have a place, I liked to give them to children who had tried hard and that was easier to maintain for me and them as I was not setting them up against their peers, nor did I need to have a race to get the stickers on. When I was following school policy and using stickers willy nilly it was obvious that the behaviours changed when I reached for the stickers rather than children wanting to behave well. Much more successful was the verbal reward " superstar" !
I tried whole class rewards, one very challenging class actually told me that as they had behaved well enough to earn their reward they didn't need to continue! (Reception!!!)
Another whole school behaviour policy to use a traffic light system with the idea that children moved from green to amber to red with sanctions on red was also difficult to maintain, some children just liked the attention of seeing their names move and really weren't bothered if they went from green to red!
I hope all that makes sense, but I suppose the real answer is you have to do what feels right for you and be consistent. I didn't like stickers and didn't feel I was consistent nor did I like whole class rewards but some people do and can make these things work. I also think the children/ cohort go a long way to making these things easy/ easier to apply and maintain.