I have 3 kids all with summer birthdays. All went to kindergarten on time. My oldest will be 15 on July 21 and will be a sophomore in the fall. She has never had any problems. My middle child turned 9 on 6/20 and while she had a few maturity problems in kindergarten, academically she has been fine.
My son turned 6 on 6/21 and will be going into first. No problems at all. I asked his pre k teacher about holding him back and she told me not to. I asked the kindergarten teacher about placing him into a transitional first grade class and was told he was fine to go on to regular first grade.
My son turned 6 on 6/21 and will be going into first. No problems at all. I asked his pre k teacher about holding him back and she told me not to. I asked the kindergarten teacher about placing him into a transitional first grade class and was told he was fine to go on to regular first grade.
I taught Pre-K and I have taught Kindergarten. I have noticed that children born in the summer months and start school "on time" seem to struggle more. I don't know if this is due to maturity or what. Understand that this is not a given. You know your child best.

It would have never occurred to me to hold my January & March kids out with a Sept. 1 cut-off and wouldn't have really thought it for my May child if it hadn't been for other issues but since the school didn't feel he needed to be held back and they dealt with him for 2 years prior, that's what we went with. For all I know my October baby will need extra help too. He already gets speech therapy (but that's because my other 2 boys needed it too so I caught his really early as I've gotten better!).