I posted an article in a similar thread that Blackrose started that made some interesting points. On phone but will link it later if you don't find it first.
One was there is a massive variety in ages children hit puberty so it doesn't necessarily hold that waiting will actually benefit in that regard.
Second was waiting a year but doing exactly same things won't necessarily lead to being more ready, growth is through experiences so depends on what they will be doing that year at home, which depends alot on personal family circumstances.
I would be inclined to listen to her daycare teachers for two reasons, 1. They have experience of many many children to reflect on. 2. I think children save their more immature behaviors for us as possible parents (as they should) so I think childcare do have a good perspective of how will go at school.
Your DD although may not have had alot of daycare has lots of exposure to other kids of differing ages through her cousins and is well travelled too. What does your DH think? What were your experiences of school - is your DD like either of you? What is the school like? They are all questions I would factor in.
I am one for keeping children back until they turn 5. Particularly if they aren't 5 until mid year. She will be up against children a whole year or more ahead of her in age/stage/maturity. I particularly took into consideration that fact when she will be younger than her peers in high school. She might be 16 1/2 and have 18 year old peers in her grade. I believe the social aspect is more important at this age (4 1/2-5) than the academics. Plus, they are babies for such a short time. Part of the reason I kept my DD back was to enjoy her for that one more year.
Ultimately for us, we wanted to give our child the best leg up we could. The way our schooling is structured in Aus, we did that by giving her the most opportunity to be able to learn and compete better. By keeping her back a year, she was more mature, had learnt more and had grown so much more socially and emotionally in the extra year she was home. She started school this year at 5 1/2 years old. She is now the top of her class, is a leader and actually helps the teacher with explaining things to her peers who don't fully grasp some concepts.
Bookmarks