I think you have to take many other factors into consideration as well! My #1 daughter was born on 25 December. She is always the youngest in class but always the tallest too. I think that's genetic. Lol. I started homeschooling her at 2 years old when she could already speak in sentences and know all her abc/123. I enrolled her into nursery at a kindergarten(3 hours session, followed moe calendar) the year she turned 4. She was on par with her peers. She took the school bus to school and even though her classmates were crying, she did not even cry and bade me goodbye because she knew what it meant by going to school. No difference academically and emotionally at this stage. In fact she was much more independent and mature as per her teachers.
But now that she is in Primary 1, things are much more different. She has her strength and weaknesses in the different subjects. I cannot say she is on par with her peers. She has classmates who are geniuses! Her school is also more demanding compared to other neighbourhood schools. The amount of homework is outrageous and depressing. She has to take higher chinese and I don't even teach chinese at home! She has never gone for any kind of academic enrichment before. Her childhood was really all about play previously. So we do see a difference between kids who have gone for enrichment vs those like me who prefers to skip all the enrichment and head outdoors with her bicycle and bubble gun everyday after school. But when she is being compared to her peers from a very ordinary neighbourhood school, she knows a lot more than them and can even complete their P3 work. I guess it all boils down to how we want to nuture our kids. And there is no right or wrong either.
I also have to admit that I feel very guilty when it comes to my #2 son because I did not spend as much time teaching him as I would like to. I need to prioritise and at this stage, guiding my P1 girl is more important because her form teachers will start calling me up if she lags behind even by one mark! So I decided to send him to school earlier which is the year he turns 3. I am very thankful for my daughter though. She has been the one teaching and reading to him ever since I got preggy with #3. Everything that he learnt, both good and bad, are mostly from her. I will only have a harder time correcting the bad..haha.. So for #3, she will most likely be an end December baby. I don't know what approach I will take yet. So just let nature take its course for now.
Oh man! I was really lor so. Hope you won't read until zzz... Lol!