I think the phrase 'holding a child back' is not how I would describe what I would like to do, although I can see how it is viewed that way by others. I just want to wait until my child is mature enough / ready for school - to move him forward at his own developmental pace instead of prematurely.
And it's not just about being worried about the longer term overall academic outcomes for summer-born children either - I'm more interested in my son's experience of his reception year. I know that he would enjoy it far more aged 5 than he would age 4, but yet a rigid system discounts that, and says 'oh, he'll be alright; he'll cope'. Everyone else manages ok.
Except they don't - I'm talking to various mums at the moment (all with children in reception year - both at school and at after-school activities) and they talk about how tired their chidren are or how their behaviour has got worse (more tantrums etc.) since they started school.
And this is not an issue of teaching skills either - I've had one teacher on facebook take my preference to delay starting my son quite personally, as though I was somehow not trusting enough of teachers' ability to be able to differentiate effectively in the classroom. This is about more than ABCs and 123s - it's being flexible enough to allow naps as needed, having one-to-one affection when wanted, feeling safe and comfortable in a home environment (along with outside activities with other children of course, e.g. toddler groups) and generally not being so 'structured' in a school setting - when he's barely 4...
I think that perhaps this doesn't make sense to lots of people because the norm today is for many children to be in structured settings from very young ages. Four years-old probably sounds quite old! But I'm not criticising that choice, I'm just saying that I wish the education system would accommodate ALL parenting styles and choices, and not just those that support or encourage school or nursery entry at what I feel is a very early age - for my child.