My mum has been part of research into readiness for school and found many boys were not considered ready until 7. In fact Finland doesn't start schooling until around 7, so much later than many of our preppies (dd will be just 5 and ds still 4).

I think a lot depends on the school too. Our local primary has a great prep program that is very similar to kinder, with play-based learning.

It's so tough. Good luck with it all.
Although my understanding from Finnish friends is that they are in full time or almost full time programs but are just not called school. Really I think that if school is not right for most 5.5 year olds then it is school that should be changing (or hours of kinder becoming more useful) to be more suitable rather than delaying starting because there are many people who can't afford to delay starting even if though it might be beneficial. I remember being in Finland and seeing classes of 3-4 year olds tramping round in the snow in their snow suits - very cute.