Our school has sticker charts, acheivement awards etc, and my son (who has some behaviour issues) has three different charts - the normal one, one for being calm, and one for not crying.
The stickers seem to be handed out to all children pretty frequently, but my son doesn't always get one. The stars get given at "golden assemblies" when children get ten stars on their chart in a week. Some children do get them more frequently than others, but then different children behave differently.
I would guess that children in the middle of the behaviour range probably do miss out. Stickers and stars are essentially used as a behaviour control tool. There isn't a "child of the week" at our school and that seems a pretty dodgy thing to me. If it's given to all children, then what's really the point? If it's for the best child, then that seems divisive. Although having said that there is a board with names on in the reception area. Maybe my son (now in year 1) has just never made it there!
Certainly at nursery my ds got vastly more stars than dd. But then she never needed any incentive for not taking her shoes off and throwing them at the teacher...
I guess what I'm saying is that there are lots of reasons why stars and stickers are used. The bad behaviour stuff is much less visible (does the school have "time outs" etc?) and may balance at least some of the stickers/stars.
However, these things should be school policy, and not up to the individual teacher. Our scheme is set out the school prospectus. You might find it useful to look at it to see if the same concerns might be true for you next year, or if it's an interpretation problem.