You've said this many times, and been answered many times.
You keep saying that what we want would disadvantage the vulnerable in society, but this completely misses the point that the CURRENT, EXISTING summer born policy and 2014 Code is ALREADY doing this.
There now ARE summer born children entering Reception class at compulsory school age; therefore the chronological age gap HAS been increased to a 17 month window in a growing number of schools over the past few years.
There are a currently some 'summer' babies, mostly August babies (not April ones) joining school in reception at just turned five (not 5.5). You've talked again, and again, about how difficult it is to convince the relevant decision makers to allow it. When you say it's going on now, it's for small numbers who have convinced people it's in the child's best interests.
That is not the same as opening the policy up to anyone, simply because they want little Johnny to be 11.5 when he sits his 11+ and 16.5 when he does his GCSEs.
My DC2 is ready to start school this year. Would she be ready if most of her contemporaries were waiting a year and lots of children were up to 5.5? No. So, like many, many middle class, educated parents, I'd defer her. So instead of being a few children who are 'old' for their year, it would end up being the vulnerable who were 'young' for their year.
I'm really not going to get into a debate about Alberta. Lots of countries have very different admission policies to ours. Those policies have to be seen in the context of the population density, the pressure on school places, the structure of schooling as a whole (when does formal learning start, do you move through the years automatically or by assessment, etc), the format of teaching and learning and many other factors. As for Gove loving Alberta, well suffice to say that's no endorsement to me coming from a family of teachers. 