and expecting the 6 year olds who had completed set work to help out
with the 5 year olds and those who hadn't.

they learn from that.

Most kids like teaching others. It's a natural instinct to give the
stragglers a hand, just as those who are more physical help the boffins
to skip and do handstands. It's the beginnings of SOCIETY!

For my daughter, who at the time had a reading age of 8+, a maturity
to match and should have been in the year ahead, this was intensely
frustrating. Children aren't stupid.

No, parents are though.

The parents should perhaps have told her that she wasn't the centre of
the universe. It's the main lesson they learn at primary school.