My first child was outgoing, confident and autumn-born. She could have coped as well with school as anybody. But even with such a child, I felt she was much too young to have people tell her exactly what to do all day.
I think the business of young children is playing. And by that I don't mean "play-based learning" in which somebody directs children's play toward a goal they wouldn't spontaneously choose. I mean that at four she still ought to be allowed to spend most of her time doing whatever she wanted, whether that was playing with soap bubbles in the sink, singing loudly while spinning in circles till she fell over, or planning an expedition to South America.
I thought a time would come when it would seem right and natural and necessary for my daughter to be sitting in a classroom receiving instruction, and then I'd send her to school. However, I've changed my mind about that! She'll be 13 in a few days' time and still seems to be reaping the benefit of a playful mindset. On the surface some of her activities have begun to resemble ones done at school, but the motivation is entirely different.
Second child, different reasons. She so clearly wouldn't meet a school's expectations of a child her age. She wouldn't manage it physically, socially, academically or emotionally. If she was really lucky and the staff were exceptionally well-motivated they might make it OKish for her by tailoring everything to her needs. It would take a big effort on everyone's part. But then what would be the point of being taught in a large group of her age peers if she was doing different PE exercises, pre-reading while they did sentence writing, counting while they multiplied? A large proportion of what she'd be exposed to would be all wrong for her. There would be constant reminders of her differences. Though everyone would make a point of speaking in positive terms about her achievements, the very environment in which she performed measurable academic tasks alongside other children would serve as a constant reminder that she couldn't do what they could do. That's if she were lucky.
If she weren't lucky, her teachers wouldn't "get" her. She'd be punished for things she couldn't help, given work she couldn't do, and would come home exhausted and frustrated. When 29 other children in class could meet the targets and she couldn't, would she decide that something was wrong with the targets or that something was wrong with her?
It could be argued that I'm just speculating and that unless she tries school we'll never know what it could be like for her. This is true. But I do know she's learning cheerfully outside of school, and I have no need to prove that school would definitely harm her. Mum's instinct tells me she is in the right place.