Red Gruffalo raises an important point which can often get lost when things get reduced to one issue at one point in time.
Children are exposed to multiple reward structures in school, and do keep track. A whole system of more personal rewards-I make a point of praising something about work in every one-on-one interaction with a learner, sticking stickers on books to mark progression (say a higher reading level) or particularly good work. My school also gives cumulative certificates for such minor rewards-something like an individual house points system. Hence achievement in itself is recognised.
Behaviour is recognised through consistent praise for the very good, and a great deal of criticism of the bad, and this is linked to tangible rewards (golden time, register taking etc.) Again, we have a cumulative aspect to this, so that for every twenty golden times you get a little chitty at circle time (this is generally lots of people).
But we also use different certificates strategically to give everyone praise for something more specific to them, the whole school assemblies or 'writer of the week' awards. It is these the OP moans about.
Hence I'm not sure it is true that a child in the 'middle' who works and behaves well has been less rewarded than a child who has lost their golden or sunshine chart for several weeks and then behaves well and gets a certificate for that. It's just that the reward is different.
Of course, whether five-year-olds report all this is different, but that doesn't mean that their reports on ONE instance actually reflect their attitudes to rewards at school-there is a world of difference between 'why do naughty kids get certificates' and 'why do naughty kids get all the praise'. I don't mind those I work with thinking the first, the latter would upset me a great deal if they absorbed it.