Delaying Entrance to Kindergarten

As a new teacher of a fourth-grade class, I wasn't sure how valid the argument for having kids with late birthdays wait a year before entering kindergarten was. However, after my first year, I noticed that almost always, the students who entered my class reading as much as two years below grade level were those with late birthdays, with the exception of a few girls. Later, when I moved to middle school, I continued to find that most of the students who were immature and having difficulty reading and/or making the transition to this level were those who were younger. Plus, they felt insecure and left out because their classmates were entering puberty.
We need to help parents realize that there is no hurry for their children to start in the academically pressured school classes that students encounter nowadays. Students will spend at least 12 years in school; they need to be ready for this experience before they start. It is imperative that they enter school with as much maturity as is possible in order for them to be successful. Why set them up for failure if we can help it? - A Teacher for 35 Years
Answer: Few studies have actually been done to examine whether or not children with birthdays between July and December do better academically when their entrance to kindergarten is delayed one year. In general, the existing studies indicate that the youngest children in a class might score slightly below the oldest, but any differences tend to be small and might fade over the years.
Parents and teachers are now accepting the idea that delaying school entrance because of age is a sound practice. The danger of this is that kindergarten programs might become developmentally inappropriate for very young children. Plus, the recommendation to hold back the youngest children will only serve to change those who will be part of the youngest group.