...The USC professor was first inspired to research this matter when he faced it as a parent.
“As my first child was about to enter kindergarten, I heard a lot from parents and school officials that children with summer birthdays, especially boys, would benefit from having a ‘year to grow’ before they start school,” Painter said. “This could give them an academic advantage and prevent them from falling behind.
“I decided that I would study this and find out if there were any academic differences in the long term,” he said. “But despite the fact that these children were a year older than their comparison group, they did not do any better.”
Delaying Kindergarten Has No Benefits
09/07/06
There are few advantages for children who wait a year to enter school, according to USC and Texas researchers.
http://www.usc.edu/uscnews/stories/12716.html