I know there have been quite a few debates here on this topic. I've tried to do some research on it. At one extreme, I read The Outliers (and read that the hockey team argument was debunked). On the other extreme, I've read the research here:
http://www.naeyc.org/files/yc/file/200309/DelayingKEntry.pdf
It's interesting because this is such a new thing, and the research is all over the place.
I have a child who was accepted to four great schools last year, for PK, even though she has a mid-August birthday. Now she's uncharacteristically quiet in her classroom. Physically she's the smallest in her class - quite a bit smaller than the other girls. The other girls seem much older than her in terms of their interests, from television to pop culture to the ways they dress and talk and play with each other. She still looks and acts like a baby compared to her classmates. I'm worried about her losing her confidence in herself. I see it every day. I hate that she's so quiet and inhibited by participating in the classroom.
But "academically" she's reading and writing pretty well and enjoying these parts of school. She follows directions and gets along pretty well in general. So I'm worried that if she repeats PK next year, she might be bored (this is according to NAEYC research). Yes, I KNOW that most of PK "academics" is really just about developing social skills, but I also feel like my daughter will be reading very very well by next year, and I'm not really sure what she might be doing when her peers are just learning their lowercase letters. (Also, I am not saying that my daughter is more brilliant than her peers, but she has older twin siblings that she is always trying to keep up with - so she is reading chapter books, etc. Her classroom seems to have a big range of readers, but thanks to her siblings she's in the lead, and I'm worried about her doing it all over again next year when she might be ready for more.)
My last worry is that the short-term effects of holding her back next year might really harm her. She's very aware of the other girls in her class, and she keeps talking about moving on to K. I don't know how we would explain it all to her.
So I'm sure this will turn into a huge debate but I'm hoping that some people might recognize my daughter's situation, and have some words of expertise for me. I just worry that my child is stressed out every day when she goes to school, and I don't know what to do. Thank you very much.