I'm in NZ and so far so good with the school system. I have one in yr3 and one in yr0 (started school in June when she turned 5). We are in a small town and it's a very good state school. I think yr0/1 has a limit of 17 per class, slightly higher numbers as they get older but still only 21 in DS's yr3 class. Just one teacher though, no teacher aide unless they come with a SEN child. As somebody said, there is flexibility as to which year a child is in - officially it is 1st July, but our school assess each child whose birthday is between April and June, and are quite keen to keep children in the lower year. They teach in groups from the start and are setting for maths from year 4. I have no idea how the curriculum compares with the UK, but it seems to me that they are a lot more relaxed and have more flexibility with what they teach. For example the whole school have been studying around the Rugby World Cup for the last term - learning about the other countries involved mainly, with a touch rugby tournament during the last few weeks. There seems to be plenty of time for sports - each term there is a sporting event (athletics, swimming sports day, cross country, winter sports) which they practise for during the term. Plus extra curricular sports of course.
It is very competitive, I find. They have prize giving at the end of each year when awards are given for academic achievement, sports achievement, etc - I find it quite odd to give a certificate to the cleverest kid in the class and the best reader, etc. DS has just done poetry recitals and that was a competition, next term there is a talent show, again there will be winners and losers. Quite different to my 'non-competitive' state school.
Our school is a bit lacking in music and drama though - I think that may be down to the head rather than the norm. And dismal foreign languages - there is no provision at all, just a smattering of Maori.
High school qualifications aren't getting a good press. They have a very complicated system that most people (including me) don't understand, so I'm just hoping they have it sorted out before DCs get there. There are more and more schools adopting international qualifications though - IB or Cambridge exams.
Interesting topic!